Phosphor, method for producing phosphor, phosphor-containing composition, light-emitting device, lighting system and image display device

ABSTRACT

To provide a yellow to orange phosphor which has high luminance and excellent temperature characteristics and which also has high luminance when mixed with a phosphor of a different color. 
     A phosphor containing a crystal phase represented by the following formula [I], wherein when its object color is expressed by the L*a*b* color system, the values of a*, b* and (a* 2 +b* 2 ) 1/2  satisfy −20≦a*≦−2, 71≦b* and 71≦(a* 2 +b* 2 ) 1/2 , respectively: 
       R 3−x−y−z+w   2 M z A 1.5x+y−w2 Si 6−w1−w2 Al w1+w2 O y+w1 N 11−y−w1   [I]

TECHNICAL FIELD

The present invention relates to a phosphor comprising anitrogen-containing compound such as a composite nitride or oxynitride,a method for producing it, a phosphor-containing composition whichcontains such a phosphor, a light-emitting device employing such aphosphor, and an image display device and lighting system provided withsuch a light-emitting device. More specifically, the present inventionrelates to a phosphor which emits a yellow to orange light underirradiation with light from an excitation light source such as asemiconductor light-emitting element being a first illuminant, a methodfor its production, a phosphor-containing composition which containssuch a phosphor, a light-emitting device with high efficiency employingsuch a phosphor, and an image display device and lighting systemprovided with such a light-emitting device.

BACKGROUND ART

In recent years, a semiconductor light-emitting device (LEDlight-emitting device) having a light source such as a light-emittingdiode (hereinafter referred to as “LED”) and a phosphor combined, hasbeen practically used. Particularly, a light-emitting device having blueLED and a cerium-activated yttrium/aluminum/garnet type yellow phosphorcombined is well used as a white-emitting device, and from such aviewpoint, a demand for a yellow phosphor is very high.

Accordingly, a research has been active for a novel yellow phosphordifferent from a conventional cerium-activated yttrium/aluminum/garnettype phosphor, and it is known that a nitride phosphor as disclosed inPatent Document 1 or 2 is particularly superior in color renderingproperties to the cerium-activated yttrium/aluminum/garnet typephosphor.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-2008-088362-   Patent Document 2: WO2008/132954

DISCLOSURE OF INVENTION Technical Problem

However, in the market of light-emitting devices as described above,development of products having higher performance is always desired.

The present invention has been made under such circumstances, and it isa first object of the present invention to obtain a phosphor having ahigher light-emitting efficiency when applied to a LED light-emittingdevice, with respect to the above-mentioned nitride type yellowphosphor. Further, another object of the present invention is to providea method for producing such a phosphor, a phosphor-containingcomposition and a light-emitting device employing such as phosphor, anda lighting system and image display device provided with such alight-emitting device.

Solution to Problem

The present inventors have conducted an extensive study to solve theabove problem and as a result, have found that when a phosphor whereinwhen its object color is expressed by the L*a*b* color system, thevalues of a*, b* and (a*²+b*²)^(1/2) are within certain specific ranges,is used for a light-emitting device, the pseudo white color emissionwill be excellent, and the color emission-efficiency will be high. Thepresent invention has been accomplished on the basis of thesediscoveries.

That is, the present invention provides the following (1) to (22).

(1) A phosphor containing a crystal phase represented by the followingformula [I], wherein when its object color is expressed by the L*a*b*color system, the values of a*, b* and (a*²+b*²)^(1/2) satisfy−20≦a*≦−2, 71≦b* and 71≦(a*²+b*²)^(1/2), respectively:

R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(w1+w2)O_(y+w1)N_(11−y−w1)  [I]

wherein R is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc; M is at least one metal elementselected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is atleast one bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical valueswithin the following ranges, respectively:

( 1/7)≦(3−x−y−z+w2)/6<(½),

0≦(1.5x+y−w2)/6<(9/2),

0≦x<3,

0≦y<2,

0<z<1,

0≦w1≦5,

0≦w2≦5,

0≦w1+w2≦5.

(2) The phosphor according to the above (1), wherein0<(1.5x+y−w2)/6<(9/2).(3) The phosphor according to the above (1) or (2), wherein the valuesof b* and (a*²+b*²)^(1/2) satisfy 71≦b*≦105 and 71≦(a*²+b*²)^(1/2)≦105,respectively(4) The phosphor according to any one of the above (1) to (3), wherein xis 0<x<3.(5) The phosphor according to any one of the above (1), (3) and (4),wherein 0≦(1.5x+y−w2)<(9/2).(6) The phosphor according to any one of above (1) to (5), wherein theabsorption efficiency is at least 88%.(7) A method for producing a phosphor containing a crystal phaserepresented by the following formula [I], which comprises nitriding analloy for production of a phosphor, containing at least elements of R, Aand Si, wherein said alloy is subjected to firing in the presence of aflux:

R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(w1+w2)O_(y+w1)N_(11−y−w1)  [I]

wherein R is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc; M is at least one metal elementselected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is atleast one bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical valueswithin the following ranges, respectively:

( 1/7)≦(3−x−y−z+w2)/6<(½),

0≦(1.5x+y−w2)/6<(9/2),

0≦x<3,

0≦y<2,

0<z<1,

0≦w1≦5,

0≦w2≦5,

0≦w1+w2≦5.

(8) The method for producing a phosphor according to the above (7),wherein 0<(1.5x+y−w2)/6<(9/2).(9) The method for producing a phosphor according to above (7), wherein0≦(1.5x+y−w2)<(9/2).(10) The method for producing a phosphor according to any one of above(7) to (9), wherein the firing is carried out under a temperaturecondition such that the rate of temperature rise during the firing is atmost 0.5° C./min within a temperature range corresponding to at least apart of the low temperature side of an exothermic peak obtainable byTG-DTA (thermogravimetry/differential thermal analysis) during thenitriding reaction of the alloy for production of a phosphor.(11) The method for producing a phosphor according to any one of above(7) to (10), wherein the firing is carried out in a hydrogen-containingnitrogen gas atmosphere.(12) The method for producing a phosphor according to any one of above(7) to (11), wherein after the firing, the obtained fired product iswashed with an acidic aqueous solution.(13) A phosphor containing a composition represented by the followingformula [I′], wherein when its object color is expressed by the L*a*b*color system, the values of a*, b* and (a*²+b*²)^(1/2) satisfy−20≦a*≦−2, 71≦b* and 71≦(a*²+b*²) respectively:

(Ln,Ca,Ce)_(3+α)Si₆N₁₁  [I′]

wherein Ln is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc, and α is a numerical value within arange of −0.1≦α≦1.5.(14) A phosphor-containing composition comprising the phosphor asdefined in any one of the above (1) to (6) and a liquid medium.(15) A light-emitting device having a first illuminant and a secondilluminant which emits visible light under irradiation with light fromthe first illuminant, wherein the second illuminant contains, as a firstphosphor, at least one phosphor selected from the group consisting ofthe phosphor as defined in any one of the above (1) to (6).(16) The light-emitting device according to the above (15), wherein thefirst phosphor has an emission peak wavelength within a wavelength rangeof from 420 nm to 450 nm.(17) The light-emitting device according to the above (15) or (16),wherein the second illuminant contains, as a second phosphor, at leastone phosphor different in the emission peak wavelength from the firstphosphor.(18) The light-emitting device according to the above (15), wherein thefirst phosphor has an emission peak within a wavelength range of from420 nm to 500 nm, and the second illuminant contains, as a secondphosphor, at least one phosphor having an emission peak within awavelength range of from 565 nm to 780 nm.(19) The light-emitting device according to the above (15), wherein thefirst phosphor has an emission peak within a wavelength range of from300 nm to 420 nm, and the second illuminant contains, as a secondphosphor, at least one phosphor having an emission peak within awavelength range of from 420 nm to 500 nm.(20) The light-emitting device according to the above (15), wherein thefirst phosphor has an emission peak within a wavelength range of from300 nm to 420 nm, and the second illuminant contains, as a secondphosphor, at least one phosphor having an emission peak within awavelength range of from 420 nm to 500 nm, at least one phosphor havingan emission peak within a wavelength range of from 500 nm to 550 nm, andat least one phosphor having an emission peak within a wavelength rangeof from 565 nm to 780 nm.(21) A lighting system provided with the light-emitting device asdefined in any of the above (15) to (20).(22) An image display device provided with the light-emitting device asdefined in any one of the above (15) to (20).

Advantageous Effects of Invention

According to the present invention, it is possible to provided a yellownitride phosphor which is superior in the pseudo white color to theconventional one and which has high luminance or luminous efficiency,when used for a light-emitting device. By using such a phosphor, it ispossible to realize a phosphor-containing composition, a light-emittingdevice with high efficiency, a lighting system and a image displaydevice.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagrammatical perspective view illustrating the positionalrelation between an excitation light source (first illuminant) and aphosphor-containing portion (second illuminant) in one embodiment of thelight-emitting device of the present invention.

Each of FIGS. 2( a) and 2(b) is a diagrammatical cross-sectional viewillustrating an embodiment of a light-emitting device having anexcitation light source (first illuminant) and a phosphor-containingportion (second illuminant).

FIG. 3 is a diagrammatical cross-sectional view illustrating anembodiment of the lighting system of the present invention.

FIG. 4 is the powder X-ray diffraction pattern of the phosphor producedin Example A1.

FIG. 5 is the powder X-ray diffraction pattern of the phosphor producedin Example A7.

DESCRIPTION OF EMBODIMENTS

Now, the present invention will be described with reference to itsembodiments or exemplifications. However, it should be understood thatthe present invention is by no means restricted to the followingembodiments or exemplifications and may be carried out as optionallychanged or modified within a range not to depart from the gist of thepresent invention. In this specification, the numerical-rangerepresented by means of “-” or “to” means the range containing thenumerical values given before and after “-” or “to” as the lower andupper limit values. Further, in this specification, the relationsbetween colors and color coordinates are all based on JIS standards (JISZ8110).

Further, in the compositional formulae of phosphors in thisspecification, the adjacent compositional formulae are delimited by acomma “,”. Further, plural elements being comma-delimited means that oneor more of such elements may be contained in any optional combinationand composition. For example, a compositional formula“(Ba,Sr,Ca)Al₂O₄:Eu” comprehensively represents all of “BaAl₂O₄:Eu”,“SrAl₂O₄:Eu”, “CaAl₂O₄:Eu”, “Ba_(1−x)Sr_(x)Al₂O₄:Eu”,“Ba_(1−x)Ca_(x)Al₂O₄:Eu”, “Sr_(1−x)Ca_(x)Al₂O₄:Eu” and“Ba_(1−x−y)Sr_(x)Ca_(y)Al₂O₄:Eu” (provided that in the above formulae,0<x<1, 0<y<1, 0<x+y<1).

[1. Phosphor of the Present Invention]

As mentioned above, the phosphor of the present invention is a phosphorcontaining a crystal phase represented by the formula [I]:

R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(w1+w2)O_(y+w1)N_(11−y−w1)  [I]

wherein R is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc; M is at least one metal elementselected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is atleast one bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical valueswithin the following ranges, respectively:

( 1/7)≦(3−x−y−z+w2)/6<(½),

0≦(1.5x+y−w2)/6<(9/2),

0≦x<3,

0≦y<2,

0<z<1,

0≦w1≦5,

0≦w2≦5,

0≦w1+w2≦5.

wherein when its object color is expressed by the L*a*b* color system,the values of a*, b* and (a*²+b*²)^(1/2) satisfy −20≦a*≦−2, 71≦b* and71≦(a*²+b*²)^(1/2), respectively.

In the following, firstly, the crystal phase represented by the formula[I] will be described in more detail.

[1-1. Composition of Crystal Phase of the Phosphor of the PresentInvention]

In the above formula [I], R is at least one rare earth element selectedfrom the group consisting of La, Gd, Lu, Y and Sc. Among them, R ispreferably at least one rare earth element selected from the groupconsisting of La, Gd and Y. Among them, R is more preferably at leastone rare earth element selected from the group consisting of La and Gd.Among them, it is particularly preferably La.

Further, as R, one rare earth element may be used alone, or two or morerare earth elements may be used in an optional combination and ratio. Byusing two or more rare earth elements as R, it is possible to change theexcitation wavelength or emission wavelength of the phosphor of thepresent invention thereby to adjust the CIE chromaticity coordinate(x,y).

However, in a case where R is composed of two or more elements, theproportion of La, a mixture of La and Gd, or a mixture of La, Gd and Y,in R is usually preferably at least 70 mol %, more preferably at least80 mol %, particularly preferably at least 95 mol %, whereby it ispossible to improve the luminance or emission intensity. Further, fromthe viewpoint of the luminance or emission intensity, the proportion ofLa based on the total amount of La, Gd and Y is usually preferably atleast 70 mol %, more preferably at least 80 mol %, particularlypreferably at least 95 mol %. Further, the proportion of the totalamount of Gd and Y based on the total amount of La, Gd and Y is usuallypreferably from 3 to 20 mol %, more preferably from 5 to 15 mol %, fromthe viewpoint of good color of yellow as the emission color.

In the above formula [I], M is at least one metal element selected fromthe group consisting of Ce, Eu, Mn, Yb, Pr and Tb. Here, M is one tofunction as an activation element. Further, as M, among the above metalelements, only one type may be used, or two or more types may be used incombination in an optional combination and ratio. Among them, M ispreferably one containing at least Ce from the viewpoint of the luminousefficiency and emission peak wavelength, and it is more preferred to useonly Ce.

With respect to Ce as an activation element, at least a part thereofwill be present in the form of a trivalent cation in the phosphor of thepresent invention. At that time, activation element Ce may taketrivalent or tetravalent valency, but the proportion of the trivalentcation should better be high. Specifically, the proportion of Ce³⁺ basedon the entire Ce amount is usually at least 20 mol %, preferably atleast 50 mol %, more preferably at least 80 mol %, particularlypreferably at least 90 mol %, most preferably 100 mol %.

Further, with respect to Eu, Mn, Yb, Pr and Tb as activation elementsother than Ce, there may be a case where cations different in thevalency coexist like in the case of Ce. By an addition of a very smallamount of such elements, there may be a case where a sensitizing effectis obtainable, and the luminance will be improved.

Here, the proportion of Ce³⁺ in the entire Ce contained in the phosphorof the present invention can be obtained by e.g. the measurement ofX-ray Absorption Fine Structure. That is, when L3 absorption edges of Ceatoms are measured, Ce³⁺ and Ce⁴⁺ exhibit separate absorption peaks, andtheir ratio can be quantified from their areas. Further, the proportionof Ce³⁺ in the entire Ce contained in the phosphor of the presentinvention can be obtained also by measurement of electron spin resonance(ESR). Further, with respect to the above M, the amount of the atom withthe desired valency can be measured by the measurement of X-rayAbsorption Fine Structure like in the case of Ce.

In the above formula [I], A is at least one bivalent metal elementselected from the group consisting of Ba, Sr, Ca, Mg and Zn. At thattime, A is preferably at least one bivalent metal element selected fromthe group consisting of Sr, Ca and Mg, more preferably Ca and Mg,further preferably Ca. Further, as the above A, only one of suchelements may be used, or two or more of them may be used in an optionalcombination and ratio.

The basic system of the crystal phase represented by the above formula[I] is a system wherein R and A coexist as surrounded by a SiN₄tetrahedron. In the crystal phase represented by the formula [I], it ispossible to increase bivalent A, while decreasing trivalent R(hereinafter this substitution will be referred to as “R−Asubstitution”). This represents a unique crystal phase, wherein theincrease of A does not correspond to the decrease of R, but the increaseof A takes place 1.5 times the reduction of R, whereby chargecompensation is carried out.

Further, in the phosphor of the present invention, a part of R may besubstituted by A by a system other than the above R−A substitution, andin such a case, N anions are substituted by O anions by the number ofsubstituted R.

Further, in the above basic system of the crystal phase, a part of Simay be substituted by Al. For this purpose, Al appears in the formula[I]. In such a case, N anions are substituted by O anions, and/orbivalent A is substituted by trivalent R.

In the above formula [I], 1.5× is a numerical value representing theamount of A substituted for a part of R by the above R−A substitution.If the value x at the time of charging before the firing is too small, abyproduct is likely to be formed during the firing. However, this valuex gradually decreases during the firing, and the final value x in thephosphor should better be small with a view to letting the phosphorundergo crystal growth to obtain high luminance. The value x at thattime is usually at most 2.5, preferably at most 2.2, more preferably atmost 1.5, in the case of utilizing a yellow emission containing areddish component. On the other hand, in the case of utilizing theyellow emission itself, it is usually at most 1.5, preferably at most1.0, more preferably at most 0.5, further preferably at most 0.2. Thelower limit of the value x may be 0 or a value exceeding 0.

In the above formula [I], y is a numerical value representing the amountof A substituted for a part of R in a system other than the above R−Asubstitution. While oxygen to be included should better be less, theremay be a case oxygen will be included slightly from the raw material orduring the firing. In such a case, N anions in the phosphor aresubstituted by O anions, and for the charge compensation, substitutionof A will be required. The value y may include 0, but is usually largerthan 0, preferably at least 0.002, more preferably at least 0.005,further preferably at least 0.008, and in the case of utilizing a yellowemission containing a reddish component, it is usually at most 2.5,preferably at most 2.2, more preferably at most 1.5. On the other hand,in the case of utilizing the yellow emission itself, it is usually atmost 1.5, preferably at most 1.0, more preferably at most 0.5, furtherpreferably at most 0.2.

In the above formula [I], z is a numerical value representing the amountof activation element M and is usually larger than 0, preferably atleast 0.002, more preferably at least 0.01, further preferably at least0.05, and usually less than 1, preferably at most 0.7, more preferablyat most 0.6. If the value z is too large, it is possible that theemission intensity decreases due to concentration quenching.

In the above formula [I], the substitution number of moles of Al isrepresented by w1 and w2. The range of this w1 is usually at least 0,preferably at least 0.002, more preferably at least 0005 and usually atmost 5, preferably at most 2, more preferably at most 1, furtherpreferably at most 0.5. On the other hand, the range of w2 is usually atleast 0, preferably at least 0.002 and usually at most 5, preferably atmost 2, more preferably at most 1, further preferably at most 0.5. Bythe substitution of Al, it is possible to adjust the color tone of theemission color of the phosphor of the present invention. Further, byadjusting w1 and w2 to be within the above ranges, it is possible toadjust the emission color while maintaining the crystal structure.

Further, in the above formula [I], the above-mentioned x, y and zsatisfy the relations of the following two relations. (1/7)≦(3−x−y−z+w2)/6<(½), and 0≦(1.5x+y−w2)/6<( 9/2).

That is, in the formula [I], “(3−x−y−z+w2)/6” represents a numericalvalue of at least 1/7 and less than ½.

Further, in the formula [I], “(1.5x+y−w2)/6” represents a numericalvalue of at least 0 and less than 9/2. And, more preferably, it islarger than 1.

Further, from the viewpoint of the emission intensity, the number ofmoles of oxygen (y+w1) in the formula [I], is preferably less than 2,more preferably less than 1.7, further preferably less than 1.5.Further, from the viewpoint of production efficiency, the above numberof moles of oxygen (y+w1) is preferably at least 0.01, more preferablyat least 0.04.

Further, from the viewpoint of the emission intensity, the number ofmoles of Al (w1+w2) in the formula [I] is usually at most 5, preferablyat most 3, more preferably at most 1. On the other hand, the lower limitis preferably close to 0, particularly preferably 0, from the viewpointof the production efficiency.

The phosphor of the present invention shows a good performance even whenit has an anion or cation deficiency to some extent. The formula [I] isa usual formula assumed to be free from a cation deficiency or an aniondeficiency. Therefore, when a deficiency is formed, there may be a casewhere x, y, z, w1 and w2 cannot be determined from the actual elementalanalytical values.

Further, in a case where the phosphor of the present invention is to beactually analyzed, the coefficients of the respective elements arelikely to include measurement errors, and there may be a case where itis difficult to separate oxygen or nitrogen adsorbed on the surface or asmall amount of impurities, and thus, it is needless to say that inreality, the values of x, y, z, w1 and w2 have allowable ranges to someextent.

Further, the phosphor of the present invention is particularlypreferably a phosphor containing a composition represented by thefollowing formula [I′], wherein when its object color is expressed bythe L*a*b* color system, the values of a*, b* and (a*²+b*²)^(1/2)satisfy −20≦a*≦−2, 71≦b* and 71≦(a*²+b*²)^(1/2), respectively:

(Ln,Ca,Ce)_(3+α)Si₆N₁₁  [I′]

wherein Ln is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc, and α is a numerical value within arange of −0.1≦α≦1.5.

Such a phosphor of the formula [I′] is essentially the same as thephosphor of the formula [I], however, in order to avoid formation ofanion deficiency or cation deficiency or as mentioned above, in the caseof actually analyzing an obtained phosphor, in order to avoid ananalytical error or formation of an impurity phase with a compositionother than the present invention in the formed phosphor or in order tointentionally avoid an influence of an impurity element, including thecase of adjusting the total amount of Ln, Ca and Ce which is essentiallyrequired, in a typical phosphor of the present invention, thecomposition within a range of the total amount of Ln, Ca and Ceallowable as the entire phosphor is defined. In such a case, −0.1≦α≦1.5is preferred, and more preferred is −0.1≦α≦1.0. Especially in a casewhere the luminance is to be improved, −0.1≦α≦0.1 is particularlypreferred.

In the phosphor of the formula [I′], the amount of N may sometimeschange to some extent for such a reason as e.g. cation deficiency oranion deficiency. When such an allowable range is represented by β, thecoefficient of N becomes 11+β. At that time, a range of −0.2≦β≦0.5 ispreferred, and more preferred is 0≦β≦0.3, and further preferred is0≦β≦0.1. The above numerical values are numerical values when the molarratio of Si is set to be 6. Further, when Si is set to be 6 mol, oxygenmay be contained in an amount of at most 1 mol, more preferably at most0.5 mol, further preferably at most 0.3 mol, particularly preferably atmost 0.1 mol, in addition to the formula [I′]. Here, from the viewpointof the analysis, oxygen is considered to be one contained in thephosphor and one adsorbed on the surface or interior of the phosphor orpresent separately from the crystals. From the viewpoint of theluminance, in the formula [I′], the amount of Ca is preferably less than2 mol, more preferably less than 1 mol, further preferably less than 0.5mol, most preferably less than 0.2 mol. In addition to theabove-mentioned adjustment of the emission color by e.g. Gd or Y, it ispossible to adjust the emission color also by the number of moles of Ca,from yellow slightly close to green, to orange, within a range of from 0to 0.5 mol.

Within the chemical composition of the above formula [I], preferredspecific examples will be given below, but it should be understood thatthe composition of the crystal phase of the phosphor of the presentinvention is by no means limited to the following examples. Within thechemical composition of the formula [I], preferred examples having nooxygen included, include the following.La_(1.37)Ce_(0.03)Ca_(2.40)Si₆N₁₁, La_(2.15)Ce_(0.10)Ca_(1.23)Si₆N₁₁,La_(2.57)Ce_(0.03)Ca_(0.60)Si₆N₁₁, La_(1.17)Ce_(0.03)Ca_(2.70)Si₆N₁₁,La_(2.68)Ce_(0.30)Ca_(0.03)Si₆N₁₁, La_(2.74)Ce_(0.20)Ca_(0.09)Si₆N₁₁,La_(2.50)Ce_(0.30)Ca_(0.30)Si₆N₁₁, La_(2.70)Ce_(0.30)Si₆N₁₁,La_(2.5)Gd_(0.20)Ce_(0.30)Si₆N₁₁, La_(2.3)Gd_(0.40)Ce_(0.30)Si₆N₁₁,La_(2.49)Gd_(0.15)Ce_(0.30)Ca_(0.09)Si₆N₁₁,La_(2.5)Y_(0.20)Ce_(0.30)Si₆N₁₁, La_(2.67)Ce_(0.03)Ca_(0.45)Si₆N₁₁,La_(2.60)Ce_(0.10)Ca_(0.45)Si₆N₁₁.

-   -   Further, preferred examples wherein oxygen is present, include        the following. La_(1.71)Ce_(0.10)Ca_(1.57)Si₆O_(0.44)N_(10.56),        La_(1.17)Ce_(0.03)Ca_(2.20)Si₆O_(1.00)N_(10.00),        La_(2.37)Ce_(0.03)Ca_(0.75)Si₆O_(0.30)N_(10.70),        La_(2.68)Ce_(0.30)Ca_(0.02)Si₆O_(0.02)N_(10.98),        La_(2.74)Ce_(0.20)Ca_(0.15)Si₆O_(0.06)N_(10.94),        La_(2.50)Ce_(0.30)Ca_(0.20)Si₆O_(0.20)N_(10.80),        La_(2.49)Ce_(0.30)Ca_(0.30)Si₆O_(0.03)N_(10.57),        La_(1.25)Ce_(0.25)Ca_(2.20)Si₆O_(0.10)N₁₀,        La_(2.66)Ce_(0.20)Ca_(0.15)Si₆O_(0.12)N_(10.88),        La_(2.61)Ce_(0.30)Ca_(0.09)Si₆O_(0.09)N_(10.91),        La_(2.57)Gd_(0.15)Ce_(0.25)Ca_(0.03)Si₆O_(0.03)N_(10.97.)

Further, a crystal phase wherein oxygen is present in a small amount,and no Ca is present, is also mentioned as preferred. In such a case,the crystal phase will be one wherein a very small portion of La or Siis deficient.

The above-described crystal phase represented by the formula [I] isessentially the one constituting a new structure (space group andsite-constituting ratio) in an alkaline earth metal element-rare earthelement (Ln)-Si—N system. Now, the difference between this crystal phaseand the crystal phases of known substances will be described.

The space group of the crystal phase represented by the above formula[I] is P4bm or its analogous space group, while the space group of knownSrYbSi₄N₇ or BaYbSi₄N₇ is P6₃mc (Zeitschrift fur Anorganische andAllgemeine Chemie, 1997, vol. 623, p. 212), and the space group of knownBaEu (Ba_(0.5)Eu_(0.5))YbSi₆N₁₁ is P2₁3 (H. Huppertz, Doctoral thesis,Bayreuth University, 1997). Thus, the crystal phase represented by theformula [I] is substantially different in the space group from the knownphosphors. Further, the crystal phase represented by the formula [I] issubstantially different from the known phosphors in the powder X-raydiffraction pattern constituting its base, and it is therefore apparentthat the crystal structure is different.

The crystal phase represented by the above formula [I] has a uniquesite-constituting ratio such that the total number of cations having alower valency than Si surrounded by SiN₄ tetrahedrons exceeds 3/6 to thenumber of SiN₄ tetrahedrons. On the other hand, in the knownCe-activated La₃Si₆N₁₁, the total number of cations having a lowervalency than Si surrounded by SiN₄ tetrahedrons is exactly 3/6 to thenumber of SiN₄ tetrahedrons (JP-A-2003-206481), and in the knownLnAl(Si_(6−z)Al_(z))N_(10−z)O_(z):Ce phosphor, the total number ofcations having a lower valency than Si surrounded by Si(or Al)N(or O)₄tetrahedrons is 2/6 to the number of Si(or Al)N(or O)₄ tetrahedrons(Patent Document 1). Thus, the crystal phase represented by the formula[I] is apparently different from the known phosphors in the constitutingratio of each site characterizing the structure.

Further, in the phosphor of the present invention, a part of theconstituting elements of the crystal phase represented by the aboveformula [I] may be deficient or may be substituted by other atoms, solong as the performance is not impaired. The following may be mentionedas examples of such other elements.

For example, in the formula [I], at the position of M, at least onetransition metal element or rare earth element selected from the groupconsisting of Nd, Sm, Dy, Ho, Er and Tm may be substituted. Among them,it is preferred that Sm and/or Tm as a rare earth element issubstituted.

Further, for example, in the formula [I], all or a part of Al may bereplaced by B. In a case where raw materials are put into a BNcontainer, followed by firing to produce a phosphor of the presentinvention, B will be included in the obtainable phosphor, and it ispossible to produce a phosphor wherein Al is replaced by B as mentionedabove. Further, for example, in the formula [I], at the positions of Oand/or N, anions such as S, Cl and/or F may be substituted.

Further, in the formula [I], a part of Si may be replaced by Ge and/orC. Such a substitution ratio is preferably at most 10 mol %, morepreferably at most 5 mol %, further preferably 0 mol %. Further, forsuch a reason that no substantial reduction of the emission strength isbrought about, at each site of R, A, Si, Al O and N in the formula [I],at most 5 mol % of an element may be substituted, or at each site, atmost 10 mol % of deficiency may be formed. However, both of suchsubstitution and deficiency should better be 0 mol %.

However, in order to obtain the merits of the present inventiondistinctly, it is preferred that the entire phosphor is made of thecrystal phase having the above-described chemical composition of theformula [I].

[1-2. Object Color of the Phosphor of the Present Invention]

The causes for coloration of inorganic crystals are generally classifiedinto the following three types. (1) Coloration due to a ligand fieldabsorption band (crystal field coloration), (2) coloration due totransition between molecular orbitals, and (3) coloration due totransition within substances having energy bands. Among them, thecoloration (1) is due to the presence of an element having an electronicstate not to completely fill the inner shell, such as a transition metalelement or a rare earth element. That is, such an incomplete inner shellhas an unpaired electron, and such an excited state imparts a color to asubstance corresponding to a visible spectrum. The emission centerelement to be used in many phosphors is a transition metal element or arare earth element and thus is provided with the requirements for (1) inconsideration of a fact that no coloration is observed in the case of amatrix crystal containing no emission center element.

From the foregoing, it is considered that as the object color of theabove phosphor, coloration unique to the phosphor is observed, since atthe same time as the light emitted from the phosphor itself uponabsorption of a visible light, light in a region where the spectralreflectance is high, is reflected. The object color is usuallyrepresented by means of the L*, a*, b* color system (JIS Z8113). Here,L* does not exceed 100, since it is usual to handle an object which doesnot emit light under irradiation light, but in the case of the phosphorof the present invention, it may exceeds 100, since the emitted light issuperimposed on the reflected light under excitation with theirradiation light source, and its upper limit is usually L*≦110. Here,the measurement of the object color of the phosphor of the presentinvention may be carried out, for example, by means of a commerciallyavailable object color measuring apparatus (such as CR-300 manufacturedby MINOLTA).

As mentioned above, the phosphor of the present invention ischaracterized in that when its object color is represented by the L*a*b*color system, the values of a*, b* and (a*²+b*²)^(1/2) satisfy−20≦a*≦−2, 71≦b* and 71≦(a*²+b*²)^(1/2), respectively.

From the viewpoint of the color, a* is usually at least −20, preferablyat least −19, more preferably at least −18, further preferably at least−17 and usually at most −2, preferably at most −5, more preferably atmost −8, further preferably at most −9, most preferably at most −11. Ifa* is too small, the color tends to be yellowish green, whereby it tendsto be difficult to perform a function as a yellow phosphor. If a* is toolarge, the color tends to be reddish yellow, whereby it tends to bedifficult to perform a function as a good yellow phosphor.

By adjusting a* to be within the above range, it is possible to obtainan object color of pure yellow. This means that in a blue color which isin a complementary relation with the yellow color, the blue light to beabsorbed is a pure blue light. Therefore, when the phosphor having a*within this range is combined with a phosphor with another emissioncolor such as a green phosphor or a bluish green phosphor to form adevice to emit the desired emission color by using blue LED as the powersource, it is possible to present a light-emitting device with highluminous efficiency, since it is thereby possible to suppress absorptionof the emission color of the second phosphor.

In such a combination of phosphors, the good characteristic relating tothis a* is an important characteristic which cannot be accomplished byyellow emission properties by a yellow phosphor alone e.g. by only afactor such as yellow light luminance. That is, in a case where a yellowphosphor and another phosphor are combined to form a light-emittingdevice, for example, among yellow phosphors having the same luminance,one having a* within this range will be excellent in the overallluminous efficiency.

Likewise, from the viewpoint of the color, b* is usually at least 71,preferably at least 72, more preferably at least 73, further preferablyat least 74, and the upper limit is not particularly limited, but isusually at most 105, preferably at most 102, more preferably at most100, further preferably at most 98. If b* is too small, the color tendsto be blackish yellow, whereby it tends to be difficult to perform afunction as a good yellow phosphor.

By adjusting b* to be within the above range, it is possible to obtainan object color of yellow which is not blackish. A substance having anobject color of blackish yellow means that it absorbs a visible lightother than the wavelength of blue light, such as in a green region or ared region, in addition to the blue color which is in a complementaryrelation with a yellow color. Therefore, when the phosphor having b*within this range and having an object color of yellow which is notblackish, is combined with a phosphor having another emission color suchas a red phosphor or a green phosphor to form a device to emit a desiredemission color such as a light bulb color emission or a warm whiteemission, by using blue LED as a light source, it is possible to providea light-emitting device having a good luminous efficiency, since it isthereby possible to substantially suppress absorption of green or redemission of the second phosphor.

In such a combination of phosphors, the good characteristic relating tothis b* is an important characteristic which cannot be accomplished byyellow emission properties by a yellow phosphor alone, e.g. by only afactor such as yellow light luminance. That is, in a case where a yellowphosphor is combined with another phosphor to form a light-emittingdevice, for example, among yellow phosphors having the same luminance,one having b* within this range will be excellent in the overallluminous efficiency.

Further, from the viewpoint of chroma, (a*²+b*²)^(1/2) is usually atleast 71, preferably at least 72, more preferably at least 74, furtherpreferably at least 76, and its upper limit is not particularly limited,but it is usually at most 105, preferably at most 102, more preferablyat most 100, further preferably at most 98. If (a*²+b*²)^(1/2) is toosmall, the color tends to be a dull color of yellow, and as(a*²+b*²)^(1/2) becomes high, the color becomes bright yellow such beingpreferred as a yellow phosphor.

By adjusting (a*²+b*²)^(1/2) to be within the above range, it ispossible to obtain an object color of dullness-free yellow. A substancehaving an object color of yellow with dullness means that it absorbsvisible light other than a blue color which is in a complementaryrelation with a yellow color, by e.g. defects in the solid substance.Therefore, when the phosphor having (a*²+b*²)^(1/2) within this rangeand having an object color of dullness-free yellow, is combined with aphosphor having another emission color, such as a red phosphor or agreen phosphor to form a device to emit a desired emission color such asa light bulb color emission or a warm white emission, by using blue LEDas a light source, it is possible to provide a light-emitting devicehaving a good luminous efficiency, since it is thereby possible tosuppress absorption of the green or red emission of the second phosphor.In such a combination of phosphors, the good characteristic relating tothis (a*²+b*²)^(1/2) is an important characteristic which cannot beaccomplished by the yellow emission properties of a yellow phosphoralone, e.g. by only a factor such as a yellow light luminance.

[1-3. Absorption Efficiency of the Phosphor of the Present Invention]

The absorption efficiency of a phosphor means a ratio of the number ofphotons absorbed by the phosphor to the number of photons of excitationlight. The absorption efficiency of the phosphor of the presentinvention is not particularly limited, but should better be high.Specifically, when the phosphor of the present invention is excited withlight having a wavelength of 455 nm, the absorption efficiency isusually at least 88%, preferably at least 89%, more preferably at least90%, further preferably at least 91%. If the absorption efficiency ofthe phosphor is too low, the amount of excitation light required toobtain the desired emission becomes large, and the energy consumptionbecomes large, whereby the luminous efficiency tends to be low. Themethod for measuring the absorption efficiency is as shown in thesection for “EXAMPLES” given hereinafter.

[1-4. Other Properties of the Phosphor of the Present Invention] [1-4-1.Emission Color]

The phosphor of the present invention usually emits yellow to orangelight. That is, the phosphor of the present invention usually becomes ayellow to orange phosphor. The chromaticity coordinate of fluorescenceof the phosphor of the present invention usually becomes a coordinatewith a region defined by (x,y)=(0.400, 0.420), (0.400, 0.590), (0.570,0.590) and (0.570, 0.420), and preferably becomes a coordinate within aregion defined by (x,y)=(0.420, 0.450), (0.420, 0.560), (0.560,0.560)and (0.560, 0.450). Therefore, in the chromaticity coordinate offluorescence of the phosphor of the present invention, the chromaticitycoordinate x is usually at least 0.400, preferably at least 0.420 andusually at most 0.570, preferably at most 0.560. On the other hand, thechromaticity coordinate y is usually at least 0.420, preferably at least0.450 and usually at most 0.590, preferably at most 0.560.

Especially when the luminance is important, the emission color ispreferably slightly greenish yellow, and in such a case, thechromaticity coordinate x being from 0.41 to 0.43, and the chromaticitycoordinate y being from 0.55 to 0.56 will be the most advantageousranges.

Here, the chromaticity coordinates of fluorescence can be calculatedfrom the after-described emission spectrum. Further, the values of theabove chromaticity coordinates x and y represent values of chromaticitycoordinates in the CIE standard coordinate system of an emission colorwhen excited with light having a wavelength of 455 nm. If a part ofelement R is substituted by another rare earth element, e.g. if a partof La is substituted by an element such as Y or Gd, it becomes possibleto control the chromaticity coordinate (x, y) values of the emissioncolor, and it becomes possible to present a width to the design ofvarious devices which will be described hereinafter.

[1-4-2. Emission Spectrum]

The spectrum (emission spectrum) of fluorescence emitted from thephosphor of the present invention is not particularly limited, but fromthe viewpoint of the application as a yellow to orange phosphor, theemission peak wavelength of the emission spectrum when excited withlight having a wavelength of 455 nm is usually at least 480 nm,preferably at least 500 nm, more preferably at least 515 nm, furtherpreferably at least 525 nm and usually at most 640 nm, preferably atmost 610 nm, more preferably at most 600 nm. Further, in a case wherethe luminance is particularly important, the emission peak wavelength ispreferably made to be from 530 nm to 535 nm.

Further, the phosphor of the present invention has a full width at halfmaximum (hereinafter sometimes referred to as “FWHM”) of an emissionpeak when excited with light having a wavelength of 455 nm, beingusually at least 100 nm, preferably at least 110 nm, more preferably atleast 115 nm. As the full width at half maximum is wide like this, thecolor rendering properties of e.g. a light-emitting device can be madegood when the phosphor of the present invention is combined with e.g.blue LED. Here, the upper limit of the full width at half maximum of theemission peak is not particularly limited, but it is usually at most 280nm.

The measurement of the emission spectrum of the phosphor of the presentinvention as well as the calculations of its luminous region, theemission peak wavelength and the full width at half value of the peakmay, for example, be carried out at room temperature (usually 25° C.) bymeans of an apparatus such as a fluorescence-measuring apparatusmanufactured by JASCO Corporation.

[1-4-3. Excitation Wavelength]

The wavelength of light to excite the phosphor of the present invention(excitation wavelength) varies depending upon e.g. the composition ofthe phosphor of the present invention. However, usually, the excitationis preferably carried out by light within a wavelength range of from anear ultraviolet region to a blue region. A specific range of theexcitation wavelength is usually at least 300 nm, preferably at least340 nm and usually at most 500 nm, preferably at most 480 nm.

[1-4-4. Weight Median Diameter]

The phosphor of the present invention preferably has a weight mediandiameter within a range of usually at least 0.1 μm, preferably at least0.5 μm and usually at most 30 μm, preferably at most 20 μm. If theweight median diameter is too small, the luminance tends to decrease,and the phosphor particles tend to agglomerate. On the other hand, ifthe weight median diameter is too large, coating irregularities orclogging of e.g. a dispenser to tend to result.

[1-5. Merits of the Phosphor of the Present Invention]

As described above, the phosphor of the present invention substantiallycontains yellowish green to orange color components and is capable ofemitting fluorescence with a wide full width at half maximum. That is,the phosphor of the present invention has a sufficient emissionintensity in a long wavelength region of from yellowish green to orangecolors, and in its emission spectrum, it is capable of emitting lighthaving an emission peak with an extremely wide full width at halfmaximum. Accordingly, when the phosphor of the present invention isapplied to a white-emitting device, such a white emitting device will becapable of emitting white light having various color tones and highcolor rendering properties, to meet with needs.

Further, the phosphor of the present invention is a phosphor which isusually particularly efficiently excited by a semiconductorlight-emitting element for near ultraviolet emission or blue emissionthereby to emit a yellowish green to orange color fluorescence. Further,the phosphor of the present invention is usually less likely to besusceptible to deterioration of emission efficiency due to a temperaturerise, as compared with a YAG:Ce phosphor which has been commonly used inwhite-emitting devices.

[1-6. Uses of the Phosphor of the Present Invention]

There is no particularly limitation to uses of the phosphor of thepresent invention. By utilizing the above merits, it may suitably beused in fields of e.g. lighting, image display devices, etc. Among them,it is suitable for the purpose of realizing particularly high outputlamps among common lighting LED, especially white LED for light bulbcolor which has high luminance and high color rendering properties andwhich has relatively low color temperature. Further, as mentioned above,the phosphor of the present invention is less susceptible todeterioration of luminous efficiency due to a temperature rise, wherebyby employing the phosphor of the present invention for a light-emittingdevice, it is possible to realize an excellent light-emitting devicewhich has high luminous efficiency and is less susceptible todeterioration of luminous efficiency due to a temperature rise and whichhas high luminance and a wide color reproduction range.

Especially, by utilizing the characteristic such that the phosphor ofthe present invention can be excited with blue light or near ultravioletlight, it can be suitably employed for various light-emitting devices(e.g. “light-emitting devices of the present invention” givenhereinafter). In such a case, by adjusting the types or proportions ofthe phosphors to be combined, it is possible to produce light-emittingdevices having various emission colors. Particularly, the phosphor ofthe present invention is usually a yellow to orange color phosphor, andaccordingly, when it is combined with an excitation light source whichemits blue light, it is possible to produce a white-emitting device. Itis thereby possible to obtain an emission spectrum similar to anemission spectrum of so-called pseudo white [e.g. emission color of alight-emitting device having blue LED and a phosphor emitting yellowfluorescence (yellow phosphor) combined].

Further, by combining a red phosphor to the above white-emitting deviceand further combining a green phosphor as the case requires, it ispossible to realize a light-emitting device excellent in red colorrendering properties or a light-emitting device which emits light bulbcolor (warm white color). In a case where an excitation light sourcewhich emits near ultraviolet light, is used, by adjusting the emissionwavelengths of a blue phosphor, a red phosphor and/or a green phosphorin addition to the phosphor of the present invention, it is possible toobtain a white light source whereby a desired emission color can beobtained.

Further, the emission color of a light-emitting device is not limited towhite color. For example, in a case where a light-emitting device isconstituted by using the phosphor of the present invention as awavelength-conversion material, it is possible to produce alight-emitting device which emits an optional color, by combining otherphosphors in addition to the phosphor of the present invention andadjusting the types or proportions of the phosphors. The light-emittingdevice thus obtained can be used as a light-emitting portion for animage display device (particularly as a backlight for liquid crystal orthe like) or as a lighting system.

Such other phosphors may, for example, be preferably phosphors whichexhibit emission of e.g. blue, bluish green, green, yellowish green, redor deep red color. Particularly, by combining the phosphor of thepresent invention, a green or red phosphor, and as an excitation lightsource, a blue-emitting diode, it is possible to constitute awhite-emitting device, such being more preferred. Further, it ispossible to constitute a preferred white-emitting device also bycombining the phosphor of the present invention with a nearultraviolet-emitting diode, a blue phosphor, a red phosphor and a greenphosphor. By adding a phosphor which emits red to deep red color to sucha white-emitting device, it is possible to further improve the colorrendering properties.

[2. Method for Producing the Phosphor of the Present Invention]

There is no particularly limitation to the method for producing thephosphor of the present invention. Any optional method may be employedso long as it is a method whereby a phosphor having the above-describedproperties can be obtained. For example, phosphor precursors areprepared as raw materials, and such phosphor precursors may be mixed asthe case requires, and the phosphor can be produced via a step (firingstep) of firing the mixed phosphor precursors. Among such productionmethods, a method is preferred wherein an alloy is used at least as apart of the raw materials. More specifically, it is preferred to producethe phosphor by a method which has a step of firing an alloy containingat least elements of R, A and Si in the above formula [I] (hereinaftersometimes referred to as “an alloy for production of a phosphor” in thepresence of a flux.

That is, the present invention provides a method for producing aphosphor containing a crystal phase represented by the following formula[I]

R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(w1+w2)O_(y+w1)N_(11−y−w1)  [I]

wherein R, M, A, x, y, z, w1 and w2 are as defined above, whichcomprises nitriding an alloy for production of a phosphor, containing atleast elements of R, A and Si, wherein said alloy is subjected to firingin the presence of a flux.

In the above production method, it is preferred to carry out the firingunder a temperature condition such that the rate of temperature riseduring the firing is at most 0.5° C./min within a temperature rangecorresponding to at least a part of the low temperature side of anexothermic peak obtainable by TG-DTA (thermogravimetry/differentialthermal analysis) during the nitriding reaction of the alloy forproduction of a phosphor. Further, it is preferred to carry out thefiring in a hydrogen-containing nitrogen gas atmosphere. Further, it ispreferred that after the firing, the obtained fired product is washedwith an acidic aqueous solution. By using such methods in combination asthe case requires, it is possible to suitably produce the phosphor ofthe present invention which has high luminance and a specific objectcolor.

Now, as an embodiment of the method for producing the phosphor of thepresent invention, the method of employing such an alloy for productionof a phosphor will be described in further detail.

[2-1. Alloy for Production of Phosphor]

As a purification method for metal simple substances to be industriallywidely used, sublimation purification, a floating zone method or adistillation method is generally known. Among such metal simplesubstances, there are many elements which are easy to purify as comparedwith metal compounds. Accordingly, a method of using required metalelement simple substances as starting materials for the production of aphosphor, alloying them and producing a phosphor from the obtained alloyfor production of a phosphor, is superior to a method of using metalcompounds as raw materials, in that it is easy to obtain raw materialshaving a high purity. Further, also from the viewpoint of uniformdispersion of activation elements in the crystal lattice, it ispreferred that the raw materials for constituting elements are metalsimple substances, whereby they may be melted and alloyed, so that theactivation elements can easily and uniformly be dispersed.

From the above viewpoint, by using, as a raw material, an alloy forproduction of a phosphor, containing at least a part of metal elementsconstituting the desired phosphor, preferably an alloy for production ofa phosphor containing all metal elements constituting the desiredphosphor, and producing a phosphor by nitriding the alloy, it ispossible to industrially produce a phosphor having a high performance.

[2-1-1. Composition of Alloy]

The alloy for production of a phosphor may be an alloy of anycomposition so long as it is an alloy containing at least elements of R,A and Si in the above formula [I]. Here, preferred types of suchelements constituting the alloy are as mentioned above.

Preferred as the alloy for production of a phosphor is one having acomposition represented by the following formula [II]:

R_(a)M_(b)A_(c)Si₆Al_(e)  [II]

wherein R is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc, M is at least one metal elementselected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb, A is atleast one bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn, and a, b, c and e represent the numerical valueswithin the following ranges, respectively: 1≦a≦4, 0≦b≦1, 0<c≦4 and0≦e≦2.

Here, preferred types of elements R, M and A in the formula [II] are thesame as in the above formula [I]. With a view to suppressing cationdefects, the value of a+b+c is more preferably at least the value of3+e/2. The alloy raw material of the formula [II] is most preferably asingle phase, but may not necessarily be a single phase, i.e. it ispossible to use one wherein to a main phase being a single phase,another phase is intimately mixed, for example, in a μm order or a 100nm order. For example, in the case of Ca_(0.45)La_(2.6)Ce_(0.1)Si₆, onewherein to a Ca_(0.3)La_(2.6)Ce_(0.1)Si₆ single phase, Ca_(0.15) isintimately mixed may be mentioned as an example.

[2-1-2. Particle Diameter of Alloy]

The average particle diameter (weight median diameter D₅₀) of an alloyfor production of a phosphor is usually at least 1 μm, preferably atleast 2 μm, more preferably at least 3 μm and usually at most 8 μm,preferably at most 7.5 μm, more preferably at most 7 μm. Even if thealloy contains a non-uniform portion, homogenization is carried out bythis pulverization step macroscopically, but microscopically, thepulverized particles having different compositions cannot be regarded asa preferred state. Therefore, it is desired that the entire alloy ishomogeneous.

[2-1-3. Contents of Carbon and Oxygen in the Alloy]

As impurities contained in the alloy, various elements are possible. Itis preferred to use, as the raw material for the production of aphosphor, an alloy wherein the carbon content is less than 1 wt %. Theupper limit is usually at most 1 wt %, preferably at most 0.3%, mostpreferably at most 0.1%, further preferably at most 0.01%. The lowerlimit is not particularly limited. However, for the stability of thequality for the production, a certain amount of at most 0.01% may beadded.

In a case where in the step of converting the alloy containing theabove-mentioned amount of carbon to a phosphor, firing is carried out inan atmosphere gas of hydrogen-containing nitrogen, the amount of carbonin the phosphor will be substantially reduced. It is considered that thecarbon in the alloy is reacted with hydrogen to form a hydrocarbon.

Further, oxygen in the alloy is likely to be included in various stepsamong steps for producing the alloy. It is preferred to use, as the rawmaterial for production of a phosphor, an alloy wherein the oxygencontent is less than 2 wt %. From the viewpoint of the luminance, theupper limit is usually less than 2 wt %, preferably at most 0.6%, morepreferably at most 0.1%. If it is too much, the oxygen contaminationamount during the firing tends to be large, whereby it tends to bedifficult to obtain the phosphor of the present invention having highluminance. The lower limit is not particularly limited.

In a case where hydrogen-containing nitrogen is used as the atmospheregas in the step of converting the alloy containing the above amount ofoxygen to a phosphor, the oxygen content in the phosphor may bemaintained or reduced. Usually, via a firing step, the amount of oxygenin the phosphor is likely to increase over the oxygen content in thestarting material in many cases, but it is considered that by conversionto CO and/or H₂O, the amount of oxygen in the phosphor is maintained orreduced. Here, the contents of carbon and oxygen in the alloy can bemeasured by the methods shown in the section of “EXAMPLES” givenhereinafter.

[2-2. Preparation of Alloy for Production of Phosphor]

The alloy for production of a phosphor having the above-describedcomposition and physical properties can be prepared as follows. Firstly,an alloy for production of a phosphor to be a raw material for aphosphor is prepared. At the time of preparing the alloy for productionof a phosphor, usually, starting materials such as metal simplesubstances, metal alloys, etc. (hereinafter sometimes referred to as“raw material metals”) are melted to obtain an alloy for production of aphosphor. In such a case, there is no limitation to the melting method,and a known melting method such as an arc melting method or a highfrequency induction heating method (a high frequency melting method)may, for example, be used.

[2-2-1. Types of Raw Material Metals]

As the raw material metals, metals, alloys of such metals, etc. may beused. Further, the raw material metals corresponding to elements whichthe phosphor of the present invention contains, may be in an optionalcombination and ratio, taking into consideration a loss such asvaporization of a part of components in the after-mentioned meltingstep. However, among the raw material metals, as the raw material metalsof metal element M being an activation element (such as the raw materialmetals corresponding to Eu, Ce, etc.), it is preferred to use Eu metalor Ce metal, since such raw materials are readily available.

The raw materials for the alloy for production of the phosphor of thepresent invention, other than the formula [II], include, for example,LaSi₂, Ce_(x)La_(1−x)Si₂ (0<x<1), LaSi, La₃Si₂, La₅Si₃, Ca₂₄Si₆₀,Ca₂₈Si₆₀, CaSi₂, Ca₃₁Si₆₀, Ca₁₄Si₁₉, Ca₃Si₄, CaSi, Ca₅Si₃, Ca₂Si,Ca_(x)La_(3−x)Si₆ (0<x<3), Ce_(y)Ca_(x)La_(3−x−y)Si₆ (0<x<3, 0<y<3),Ca₇Si, Ca₂Si, Ca₅Si₃, CaSi, Ca₂Si₂, Ca₁₄Si₁₉, Ca₃Si₄, SrSi, SrSi₂,Sr₄Si₇, Sr₅Si₃, Sr₇Si, etc. Further, an alloy containing Si, aluminumand an alkaline earth metal may, for example, be one having alloy phasesof e.g. Ca(Si_(1−x)Al_(x))₂, Sr(Si_(1−x)Al_(x))₂, Ba(Si_(1−x)Al_(x))₂and Ca_(1−x)Sr_(x)(Si_(1−y)Al_(y))₂ suitably combined. Particularly,LaSi, La₃Si₂, La₅Si₃ and an alloy having a part of its La positionsubstituted by Ce, are preferred. Among them, LaSi is preferred, sincethe ratio of La is low, whereby the safety in handling is high. In sucha case, in order to obtain La₃Si₆N₁₁ crystal, Si₃N₄ tends to bedeficient, and it is necessary to heat the raw material having a siliconsource added, to prepare the phosphor. As such a silicon source, Si₃N₄is preferred.

[2-2-2. Purity of Raw Material Metals]

The purity of metals to be used as raw material metals for the alloy forproduction of a phosphor should better be high. Specifically, from theviewpoint of the emission characteristics of the phosphor to beprepared, as a raw material metal corresponding to activation element M,it is preferred to use a metal purified to such an extent thatimpurities are usually at most 0.1 mol %, preferably at most 0.01 mol %.Further, also a metal to be used as a raw material metal for an elementother than activation element M preferably has an impurity concentrationof at most 0.1 mol %, more preferably at most 0.01 mol %, for the samereason as in the case of activation element M. For example, when atleast one member selected from the group consisting of Fe, Ni and Co iscontained as an impurity, the content of each impurity element isusually at most 500 ppm, preferably at most 100 ppm.

[2-2-3. Shape of Raw Material Metals]

There is no particularly limitation to the shape of raw material metals,but usually, granular or massive ones having a diameter of from a few mmto a few tens mm are used. Here, ones having a diameter of at least 10mm are referred to as massive, and ones having a diameter less than 10mm are referred to as granular.

Further, raw material metals corresponding to alkaline earth metalelements are not concerned about their shapes such as granular ormassive shapes, and a proper shape is preferably selected depending uponthe chemical nature of the particular raw material metals. For example,Ca is stable and useful in the atmospheric air in either granular ormassive form, while Sr is chemically more active, and therefore it ispreferred to use a massive raw material.

Further, a metal element to be lost by its evaporation during themelting or its reaction with a crucible material, may be preliminarilyexcessively weighed and used, as the case requires.

[2-2-4. Melting of Raw Material Metals]

After weighing raw material metals, such raw material metals are meltedand alloyed to produce an alloy for production of a phosphor (meltingstep). At the time of melting the raw material metals, there is thefollowing problem, particularly in the case of producing an alloy forproduction of a phosphor containing Si, rare earth element and analkaline earth element.

The melting point of Si is 1,410° C., which is the same level as theboiling point of an alkaline earth metal (e.g. the boiling point of Cais 1,494° C., the boiling point of Sr is 1,350° C. and the boiling-pointof Ba is 1,537° C.). Therefore, there has been a problem such that thealkaline earth metal-undergoes evaporation during the melting, wherebyan alloy having the desired composition cannot be obtained.

Therefore, in the present invention, the composition of the alloy to beformed is controlled by utilizing the nature of an eutectic pointcomposition of Si and rare earth element alloy, e.g. in the case of aSi—La type alloy, the eutectic point temperature of LaSi₂ is 1,205° C.which is lower than the melting point of Si simple substance. That is,it has been found possible to obtain an alloy having a prescribedcomposition by firstly arranging so that an alloy with a compositionhaving a melting point close to the eutectic point will be formed first,for example, by arranging the charging so that (La, Ca)Si₂ will beformed first and then, the rest of metals will be melted therein, andthus, the above problem has been solved. Further, there will be such aneffect that the purity of the obtainable alloy will be improved, and theproperties of a phosphor prepared by using it as the raw material willbe remarkably improved.

The obtainable alloy for production of a phosphor is one containing atleast elements of R, A and Si among metal elements constituting thephosphor of the present invention, and is preferably one having acomposition represented by the above formula [II]. Further, even in acase where one alloy for production of a phosphor does not contain allof the metal elements to constitute the phosphor of the presentinvention, it is possible to produce the phosphor of the presentinvention by using two or more alloys for production of phosphors and/orother raw materials (such as metals) in combination in the subsequentfiring step.

There is no particularly limitation to the method for melting rawmaterial metals, and an optional method may be adopted. For example, itis possible to employ a resistance heating method, an electron beammethod, an arc melting method, a high frequency induction heating method(high frequency melting method) or the like. Further, two or more ofsuch methods may be used in an optional combination for the melting.

Further, the material for a crucible useful for the melting may, forexample, be alumina, calcia, graphite, molybdenum, boron nitride oriridium. Further, to prevent inclusion of the crucible material, it ispossible to employ a high frequency melting method employing awater-cooled copper crucible (so-called scull melting method or coldcrucible melting method). This method is very preferable as a method forproducing an alloy for the present phosphor, of which the melting pointexceeds 1,500° C.

However, in the case of producing an alloy for production of a phosphorcontaining metal elements which cannot be melted simultaneously, such asSi and alkaline earth metal elements, the alloy for production of aphosphor may be produced by producing a matrix alloy and then mixingother metal raw materials. For a detailed method in such a case,WO2006/106948 may be referred to.

In the case of melting any raw material metal, with respect to thespecific temperature condition and melting time at the time of meltingthe raw material metal, a suitable temperature and time may be setdepending upon the raw material metal to be used. Further, theatmosphere during the melting of the raw material metal is optional solong as an alloy for the production of a phosphor is thereby obtainable,but an inert gas atmosphere is preferred, and an argon atmosphere isparticularly preferred. Here, one of inert gases may be used alone, ortwo or more of them may be used in an optional combination and ratio.Further, the pressure during the melting of the raw material metals isoptional so long as an alloy for production of a phosphor can thereby beobtainable, but it is preferably at least 1×10³ Pa and preferably atmost 1×10⁵ Pa. Further, also from the viewpoint of safety, it ispreferred to carry out the melting under atmospheric pressure or lower.

[2-2-5. Casting of Melt]

By the above-described melting of raw material metals, an alloy forproduction of a phosphor is obtained. This alloy for production of aphosphor is obtained usually as an alloy melt, however, there are manytechnical problems to directly produce a phosphor from such an alloymelt. Therefore, it is preferred to obtain a solidified product(hereinafter sometimes referred to as an “alloy lump”) via a castingstep wherein the alloy melt is cast in a mold.

However, there may be a case where in this casting step, segregationresults by a cooling speed of molten metals, whereby the alloy forproduction of a phosphor having a uniform composition in a molten stateis likely to have a deviation in the distribution of the composition.Accordingly, the cooing speed should better be fast. Further, the moldis preferably made of a material having good thermal conductivity suchas copper, and is preferably in a shape to readily release the heat.Further, as the case requires, it is also preferred to cool the mold bysuch a means as cooling with water.

As such an idea, it is, for example, preferred that by using a moldhaving a large bottom surface to the thickness, the melt is solidifiedas quickly as possible after being poured into the mold.

Further, the degree of such deviation varies depending upon thecomposition of the alloy for production of a phosphor, and it ispreferred that by sampling samples from several portions of the obtainedsolidified product and carrying out an analysis of the composition bymeans of a necessary analyzing means such as an ICP emissionspectroscopic analysis, the cooling speed required to prevent thesegregation is determined.

Further, the atmosphere during the casting is preferably an inert gasatmosphere, particularly preferably an argon atmosphere. At that time,one of such inert gases may be used alone, or two or more of them may beused in an optional combination and ratio.

[2-2-6. Pulverization of Alloy Lumps]

The alloy for production of a phosphor may be in the form of lumps, orpowder. However, in the form of lumps, the reaction to form a phosphortends to hardly proceed, and therefore, it is preferred to pulverizethem to a predetermined particle diameter, prior to the firing.Therefore, the alloy lumps obtained by the casting are pulverized(pulverization step) to obtain a powder of an alloy for production of aphosphor (hereinafter sometimes referred to as an “alloy powder”) havingthe desired particle diameter and particle size distribution.

Here, from the viewpoint of the production of a phosphor having highluminance and safe raw materials, if the particle diameter of the alloyis too large, nitriding tends to hardly take place, whereby theluminance of the obtainable phosphor tends to be low. Further, if it istoo small, in the pulverization step of the powder, a danger of ignitionof the powder increases due to leakage of the powder into theatmospheric air or leakage of the atmospheric air to the powder, and atthe same time, deterioration of the luminance is likely to occur due toan increase of the oxygen contamination amount.

The pulverization method is not particularly limited, and for example,the pulverization can be carried out by a dry method or a wet methodusing an organic solvent such as ethylene glycol, hexane or acetone.

Now, the method will be described in detail with reference to the drymethod. This pulverization step may be carried out dividedly in aplurality of steps such as a roughly pulverizing step, an intermediatelypulverizing step and a finely pulverizing step, as the case requires. Insuch a case, in all pulverization steps, the same apparatus may be usedfor pulverization, but the apparatus may be changed depending upon theparticular step.

Here, the roughly pulverizing step is a step of pulverization so thatabout 90 wt % of the alloy powder will have a particle diameter of atmost 1 cm, and for example, a pulverization apparatus such as a jawcrusher, a gyratory crusher, a crushing roll or an impact crusher may beused. The intermediately crushing step is a step of pulverization sothat about 90 wt % of the alloy powder will have a particle diameter ofat most 1 mm, and for example, a pulverization apparatus such as a corncrusher, a crushing roll, a hammer mill or a disk mill may, for example,be used. The finely pulverizing step is a step of pulverization so thatthe alloy powder will have the after-mentioned weight median diameter,and for example, a pulverizing apparatus such as a ball mill, a tubemill, a rod mill, a roller mill, a stamp mill, an edge runner, avibration mill or a jet mill may be used.

With a view to preventing inclusion of impurities, in the finalpulverization step, it is preferred to use a jet mill. To use a jetmill, the alloy lumps are preferably preliminarily pulverized to aparticle diameter of at most about 2 mm. In a jet mill, pulverization ofparticles is carried out by utilizing the expansion energy of a fluidjetted from the nozzle initial pressure to the atmospheric pressure,whereby it is possible to control the particle diameter by thepulverization pressure and to prevent inclusion of impurities. Thepulverization pressure varies depending upon the apparatus, but it isusually at least 0.01 MPa, preferably at least 0.05 MPa, more preferablyat least 0.1 MPa and usually at most 2 MPa, preferably at most 0.4 MPa,more preferably at most 0.3 MPa, by gauge pressure. If the gaugepressure is too low, the particle diameter of the obtainable particlesis likely to be too large, and if it is too high, the particle diameterof the obtainable particles is likely to be small.

In any case, it is preferred to properly select the relation between thematerial of the pulverizer and the object to be pulverized so as toavoid inclusion of impurities such as iron during the pulverizationstep. For example, the portion in contact with the powder preferably hasa ceramic lining applied, and among ceramics, alumina, silicon nitride,tungsten carbide or zirconia may, for example, be preferred. Here, theymay be used alone, or two or more of them may be used in an optionalcombination and ratio.

In order to prevent oxidation of the alloy powder, it is preferred tocarry out the pulverization step in an inert gas atmosphere. The type ofthe inert gas is not particularly limited, but usually, it is possibleto use a single atmosphere of one gas among nitrogen, argon, helium,etc. or a mixed atmosphere of two or more such gases. Among them,nitrogen is particularly preferred from the viewpoint of the economicalefficiency.

The oxygen concentration in the atmosphere is not particularly limitedso long as oxidation of the alloy powder can be prevented, but it isusually at most 10 vol %, particularly preferably at most 5 vol %.Further, the lower limit of the oxygen concentration is usually about 10ppm. It is considered that by adjusting the oxygen concentration to bewithin the specified range, an oxidized coating film will be formed onthe surface of the alloy during the pulverization, whereby the powderwill be stabilized. In a case where the pulverization step is carriedout in an atmosphere wherein the oxygen concentration is higher than 5vol %, it is possible that the powder dust will explode during thepulverization, and therefore, it is preferred to provide an equipmentnot to let such powder dust be formed.

Further, cooling may be applied, as the case requires, to prevent atemperature rise of the alloy powder during the pulverization step.

[2-2-7. Classification of Alloy Powder]

The alloy powder obtained as described above is preferably adjusted tohave the desired weight median diameter D₅₀ and particle sizedistribution (classification step) by means of e.g. a sieving apparatususing a mesh such as a vibration screen or a shifter; an inertialclassification apparatus such as an air separator; or a centrifugalseparator such as a cyclone, and then subjected to the subsequent steps.

Here, in the adjustment of the particle size distribution, it ispreferred that coarse particles are classified and recycled to thepulverizer, and it is more preferred that the classification and/or therecycling is continuous.

The classification step is also preferably carried out in an inert gasatmosphere. The type of the inert gas is not particularly limited, butusually, a single atmosphere of one gas among nitrogen, argon, helium,etc. or a mixed atmosphere of two or more such gases, is used andnitrogen is particularly preferred from the viewpoint of the economicalefficiency. Further, the oxygen concentration in the inert gasatmosphere is preferably at most 10 vol %, particularly preferably atmost 5 vol %.

[2-2-8. Preparation of the Alloy by Atomizing Method or the Like]

The alloy for production of a phosphor may be produced via the followingsteps (a) to (c), other than the production by the above-describedmethod. It is thereby possible to obtain a powder of an alloy forproduction of a phosphor having an angle of repose of at most 45°. (a)Two or more among raw material metals corresponding to the metalsconstituting the phosphor are melted to prepare an alloy melt containingsuch elements (melting step). (b) The alloy melt is atomized in an inertgas (atomizing step). (c) The atomized alloy melt is solidified toobtain an alloy powder (solidification step).

That is, this method is one wherein the alloy melt is atomized in a gas,followed by solidification to obtain a powder. The above atomizing step(b) and the solidification step (c) are preferably carried out, forexample, by a method of spraying the alloy melt, a method of quenchingby means of a roll or a gas stream to finely form the alloy melt into aribbon, or an atomizing method to obtain a powder. Among them, it ispreferred to employ an atomizing method. Specifically, a known methoddisclosed in WO2007/135975 may be employed by suitable modification asthe case requires.

[2-3. Firing Step]

The obtained alloy for production of a phosphor is fired in the presenceof flux and nitrided to obtain a phosphor of the present invention.Here, the firing is preferably carried out in a hydrogen-containingnitrogen gas atmosphere, as described hereinafter.

[2-3-1. Mixing of Raw Materials]

In a case where the composition of metal elements contained in the alloyfor production of a phosphor agrees to the composition of metal elementscontained in the crystal phase represented by the formula [I], only thealloy for production of a phosphor may be fired. On the other hand, in acase where they do not agree, the alloy for production of a phosphor ismixed with an alloy for production of a phosphor, metal simplesubstances, metal compounds, etc. having another composition to adjustso that the composition of metal elements contained in the raw materialswill agree to the composition of metal elements contained in the crystalphase represented by the formula [I], and then the firing is carriedout.

Here, even in a case where the composition of metal elements containedin the alloy for production of a phosphor agrees to the composition ofmetal elements contained in the crystal phase represented by the formula[I], if a nitride or oxynitride (which may be a nitride or oxynitridecontaining an activation element of the phosphor of the presentinvention itself) is mixed to the alloy for production of a phosphor, itbecomes possible to suppress the heat generation rate per unit volumeduring the nitriding thereby to let the nitriding reaction proceedsmoothly, as disclosed in WO2007/135975, whereby it becomes possible toobtain a phosphor having high properties at a high productivity. For theproduction of the phosphor of the present invention, the nitridingtreatment may be carried out in the presence of a suitable nitride oroxynitride with reference to WO2007/135975 with suitable modificationsas the case requires.

At that time, there is no particular limitation to metal compounds whichmay be used as mixed to the alloy for production of a phosphor, and forexample, a nitride, an oxide, a hydroxide, a carbonate, a nitrate, asulfate, an oxalate, a carboxylate, a halide, etc. may be mentioned.Specific types may suitably be selected among these metal compounds inconsideration of e.g. low generation of NO_(x) or SO_(x) during thefiring or the reactivity to the desired product. However, from such aviewpoint that the phosphor of the present invention is anitrogen-containing phosphor, it is preferred to use a nitride and/oroxynitride. Among them, it is particularly preferred to employ anitride, since it also plays a role as a nitrogen source.

Specific examples of the nitride and oxynitride include nitrides ofelements constituting the phosphor, such as AlN, Si₃N₄, Ca₃N₂, Sr₃N₂,EuN, etc., and composite nitrides of elements constituting the phosphor,such as CaAlSiN₃, (Sr,Ca)AlSiN₃, (Sr,Ca)₂Si₅N₈, CaSiN₂, SrSiN₂, BaSi₄N₇,etc. Further, the above nitrides may contain a very small amount ofoxygen. In the nitrides, the ratio (molar ratio) ofoxygen/(oxygen+nitrogen) is optional so long as the phosphor of thepresent invention is thereby obtainable, but it is usually at most 5%,preferably at most 1%, more preferably at most 0.5%, further preferablyat most 0.3%, particularly preferably at most 0.2%. If the ratio ofoxygen in a nitride is too much, the luminance is likely to be low.

The weight median diameter D₅₀ of a metal compound is not particularlylimited so long as there is no trouble in mixing with other rawmaterials. However, it is preferably readily mixed with other rawmaterials, and for example, it is preferably at the same level as thealloy powder. The specific value for the weight median diameter D₅₀ of ametal compound is optional so long as the phosphor can be obtained, butit is preferably at most 200 μm, more preferably at most 100 μm,particularly preferably at most 80 μm, further preferably at most 60 μmand preferably at least 0.1 μm, more preferably at least 0.5 μm.Further, each of the above-mentioned alloy for production of a phosphor,metal simple substance, metal compound, etc. may be used alone, or twoor more of them may be used in an optional combination and ratio.

It is preferred that an alloy for production of a phosphor, containingall of metal elements to constitute a phosphor, is prepared, and aphosphor is produced by firing such an alloy, whereby it is possible tosimply produce a good phosphor in a small number of steps. Further, in aconventional production method wherein an alloy is not used, there hasbeen a case where a phosphor having a desired element composition ratiocannot be obtained as the compositional ratio of the metal elementscontained in the raw materials has changed by e.g. the firing. Whereas,by using an alloy for production of a phosphor, it is possible to simplyobtain a phosphor having the desired compositional ratio simply bycharging metal elements along the stoichiometry of the desired phosphor.

[2-3-2. Flux]

In the firing step, it is preferred that a flux is permitted to coexistin the reaction system with a view to letting good crystals grow.

The type of the flux is not particularly limited, and it may, forexample, be ammonium halide such as NH₄Cl or NH₄F.HF; an alkali metalcarbonate such as NaCO₃ or LiCO₃; an alkali metal halide such as LiCl,NaCl, KCl, CsCl, LiF, NaF, KF or CsF; an alkaline earth metal halidesuch as CaCl₂, BaCl₂, SrCl₂, CaF₂, BaF₂, SrF₂, MgCl₂ or MgF₂; analkaline earth metal oxide such as BaO; boron oxide, boric acid or analkali metal or alkaline earth metal borate compound such as B₂O₃, H₃BO₃or Na₂B₄O₇; a phosphate compound such as Li₃PO₄ or NH₄H₂PO₄; an aluminumhalide such as AlF₃; a zinc compound such as a zinc halide such as ZnCl₂or ZnF₂, or zinc oxide, a compound of a Group 15 element of the PeriodicTable, such as Bi₂O₃ or a nitride of an alkali metal, alkaline earthmetal or Group 13 element, such as Li₃N, Ca₃N₂, Sr₃N₂, Ba₃N₂ or BN.

Further, the flux may, for example, be a halide of a rare earth element,such as LaF₃, LaCl₃, GdF₃, GdCl₃, LuF₃, LuCl₃, YF₃, YCl₃, ScF₃ or ScCl₃,or an oxide of a rare earth element, such as La₂O₃, Gd₂O₃, Lu₂O₃, Y₂O₃or Sc₂O₃.

As the above flux, a halide is preferred, and specifically, a halidesuch as an alkali metal halide, an alkaline earth metal halide, a halideof Zn or a halide of a rare earth element, is preferred. Further, amonghalides, a fluoride or a chloride is preferred, and further preferred isa fluoride. Specifically, an alkali metal fluoride, an alkaline earthmetal fluoride, ZnF₂ or a fluoride of a rare earth element, ispreferred, and particularly preferred is a rare earth metal fluoride oran alkaline earth metal fluoride.

Here, an anhydride should better be used for one having a deliquescentnature among the above fluxes. Further, one of the fluxes may be usedalone, or two or more of them may be used in an optional combination andratio.

As a further preferred flux, MgF₂ may be mentioned, but other than that,CeF₃, LaF₃, YF₃ or GdF₃ may also be suitably used. Among them, YF₃,GdF₃, etc. have an effect to change the chromaticity coordinate (x,y) ofthe emission color. In a case where CeF₃ is used, Ce being a lightemission center may not be contained in the raw material (an alloy or amixture of an alloy with a nitride) constituting the matrix crystal,such being desirable. When Ce is incorporated in the alloy, it may belocalized by e.g. segregation, since its amount is small. Accordingly,from the viewpoint of the stability for the production, it isparticularly preferred to use CeF₃.

The amount of the flux to be used varies depending on the type of theraw material or the material for the flux and is optional, but it isusually within a range of at least 0.01 wt %, preferably at least 0.1 wt%, more preferably at least 0.3 wt % and usually at most 20 wt %,preferably at most 10 wt %, based on the entire raw material. If theamount of the flux is too small, the effect of the flux may not beobtained, and if the amount of the flux is too much, the effect of theflux is likely to be saturated, or it is likely to be included in thematrix crystal to change the emission color or to bring aboutdeterioration of the luminance, or to bring about deterioration of thefiring furnace.

[2-3-3. Heating Conditions]

The alloy powder thus obtained and other compounds added, as the caserequires, are usually filled in a crucible or a container such as atray, which is then set in a heating furnace capable of controlling theatmosphere. At that time, as the material for the firing container to beused here, boron nitride, silicon nitride, carbon, aluminum nitride,molybdenum or tungsten may, for example, be mentioned, since thereactivity with the metal compounds is low as the material for thecontainer. Among them, molybdenum or boron nitride is preferred, sinceit is excellent in corrosion resistance. Further, one of such materialsmay be used alone, or two or more of them may be used in an optionalcombination and ratio.

The shape of the firing container to be used here is optional. Forexample, the bottom surface of the firing container may be no angularshape such as circular or oval, or a polygonal shape such as triangularor square, and the height of the firing container is also optional solong as acceptable in the heating furnace and may be low or high. It ispreferred to select a shape which presents a good heat releasingproperty.

And, by heating the alloy powder, the phosphor of the present inventioncan be obtained. Here, the alloy powder is preferably fired in a statewhere it is held at a volume filling rate of at most 40%. Here, thevolume filling rate can be obtained by (bulk density of the mixedpowder)/(theoretical density of the mixed powder)×100[%].

The firing container filled with such a raw material for a phosphor isset in a firing apparatus (hereinafter sometimes referred to as “aheating furnace”). The firing apparatus to be used here is optional solong as the effects of the present invention can be obtained, but anapparatus capable of controlling the atmosphere in the apparatus ispreferred, and an apparatus capable of controlling also the pressure isfurther preferred. For example, a hot isostatic press apparatus (HIP) ora resistance-heating type vacuum pressure atmosphere thermal treatmentfurnace is preferred. Further, it is preferred that before initiation ofthe heating, a gas containing nitrogen is permitted to flow in thefiring apparatus to sufficiently replace the interior of the system withthis nitrogen-containing gas. As the case requires, after evacuating theinterior of the system, the nitrogen-containing gas may be introduced.

As the nitrogen-containing gas to be used for the nitriding treatment, agas containing nitrogen element such as nitrogen, ammonia or a mixed gasof nitrogen and hydrogen, may, for example, be mentioned. Further, oneof such nitrogen-containing gases may be used alone, or two or more ofthem may be used in an optional combination and ratio. Among them, anitrogen gas containing hydrogen (hydrogen-containing nitrogen gas) ispreferred as the nitrogen-containing gas. Here, the mixing proportion ofhydrogen in the hydrogen-containing nitrogen gas is preferably at most 4vol %, since this is outside the explosion limit and thus is safe.

The first effective reason as to why it was possible to realize anitride yellow phosphor having high luminance and a specific objectcolor by employing an alloy as the raw material, and the hydrogengas-containing nitrogen gas, is considered to be as follows. That is, inorder for the metal to be nitrided, nitrogen molecules are required tobe dissociated, and it is considered that hydrogen radicals are formedon the alloy surface, and they assist the dissociation of the nitrogenmolecules to accelerate nitriding of the alloy by dissociated nitrogen.It is known that when nitrogen atoms in a gas phase are dissociated andadsorbed on the surface of a metal such as a transition metal, Hradicals assist such dissociation and adsorption, whereby NHx specieshaving two atomic molecules of nitrogen dissociated, will be readilyformed on the surface.

Further, as the second reason as to why it was possible to realize thehigh luminance and the specific object color, it is considered thathydrogen in the gas phase is reacted with a small amount of carbonduring the firing to suppress the amount of carbon in the phosphorthereby to suppress deterioration of the luminance due to the coexistingcarbon. After the firing under N₂—H₂, it was confirmed that the amountof carbon in the solid was reduced to a half. Thus, it is consideredthat in a case where the alloy is used as the raw material, coexistenceof hydrogen atoms in addition to nitrogen atoms presents good effects toremove carbon and to assist good nitriding with less nitrogendeficiency. In that sense, it is also preferred to use ammonia gascontaining both nitrogen atoms and hydrogen atoms, so long as gastightness of the firing furnace is ensured.

The oxygen concentration in the system is influential over the oxygencontent of the phosphor to be produced, and if the content is too high,high luminance tends to be hardly obtainable. Accordingly, the oxygenconcentration in the atmosphere for nitriding treatment should better below, and it is usually at most 0.1 vol %, preferably at most 100 ppm,more preferably at most 10 ppm, further preferably at most 5 ppm.Further, as the case requires, the oxygen concentration may be loweredby introducing an oxygen getter such as carbon or molybdenum into theheating portion in the system. Here, one of oxygen getters may be usedalone, or two or more of them may be used in an optional combination andratio.

The nitriding treatment is carried out by heating the phosphor rawmaterial in a state where the hydrogen-containing nitrogen gas is filledor is permitted to flow, and the pressure at that time may be slightlylower than the atmospheric pressure, or equal or higher than theatmospheric pressure. However, to prevent inclusion of oxygen in theatmospheric air, the pressure is preferably at least the atmosphericpressure. If the pressure is lower than the atmospheric pressure, if theair tightness of the heating furnace is poor, a large amount of oxygenwill be included, whereby it may be difficult to obtain a phosphorhaving good properties. The pressure of the hydrogen-containing nitrogengas is preferably at least 0.1 MPa (at least ordinary pressure) by gaugepressure. Otherwise, it is also possible to carry out the heating undera high pressure of at least 20 MPa. The pressure is preferably at most200 MPa. Thereafter, a gas containing nitrogen is permitted to flow tosufficiently replace the inside of the system with this gas. As the caserequires, after evacuating the inside of the system, the gas may beintroduced.

By the way, the nitriding reaction of a metal is usually an exothermicreaction. Accordingly, during the production of a phosphor by analloying method, it is possible that due to a reaction heat dischargedabruptly, the alloy is re-melted, and the surface area decreases. If thesurface area decreases like this, the reaction between the nitrogen gasand the alloy may be delayed. For this reason, in the alloying method,it is preferred to maintain the reaction rate at which the alloy willnot be melted, so that a high performance phosphor can constantly beproduced. Particularly, it is preferred to carry out the firing byraising the temperature at a low rate of at most 1.5° C./min at least ina temperature region of the rising of the exothermic peak in the firingtemperature region of from 1,150 to 1,400° C. where the heat generationof the nitriding is vigorous. The upper limit in the temperature-raisingrate is usually at most 1.5° C./min, preferably at most 0.5° C./min,more preferably at most 0.1° C./min. Further, the lower limit is notparticularly limited and may be determined from the economical viewpointfor industrial production. Here, the exothermic peak is an exothermicpeak obtainable by TG-DTA (thermogravimetry/differential thermalanalysis).

By this method, it is possible to suppress abrupt generation of thenitriding heat of the alloy and it is possible to suppress a localtemperature rise and to obtain a good phosphor, and at the same time, bysetting a high temperature raising rate in another temperature regionwhere no nitriding heat is generated, it is possible to accomplishefficient production of a phosphor wherein the overall firing time isshortened.

Further, the heating temperature varies also depending upon e.g. thecomposition of the alloy for production of a phosphor, but it is usuallyat least 1,000° C. and at most 1,800° C., more preferably at least1,400° C. and at most 1,700° C. Here, the temperature means thetemperature in the furnace during the heat treatment, i.e. the settemperature of the firing apparatus.

In a case where a phosphor is prepared by nitriding an alloy,heretofore, no flux was added at the stage of nitriding the alloy, andafter nitriding the alloy, particles were grown in the presence of aflux at the time of the second firing. Advantages of the nitriding thealloy in the presence of a flux in the present invention will bedescribed. Firstly, this nitride phosphor easily loses luminance ifoxygen is included during the preparation, but by limiting the firing toonce, it is possible to prevent inclusion of oxygen by oxidation of aninstable byproduct due to contact with the atmospheric air. Secondly,melting or partial evaporation of the flux during the firing will bringabout the effect to reduce the nitriding heat of the alloy thereby tosuppress a local temperature rise and contribute to the synthesis ofgood phosphor particles. Thirdly, crystal growth will start in thepresence of the flux from the nitrided portion, whereby efficientcrystal growth will be accomplished, such being advantageous for highluminance.

The heating time (retention time at the maximum temperature) for thenitriding treatment may be a time required for the reaction between thephosphor raw material and nitrogen, and it is usually at least 1 minute,preferably at least 10 minutes, more preferably at least 30 minutes,further preferably at least 60 minutes. If the heating time is shorterthan 1 minute, the nitriding reaction may not be completed, and aphosphor having good properties may not be obtained. Here, the upperlimit for the heating time is determined from the viewpoint of theproduction efficiency, and it is usually at most 50 hours, preferably atmost 24 hours.

In the production method of the present invention, as the case requires,the alloy for production of a phosphor may preliminarily be nitrided(primary nitriding), and then, the above-described nitriding treatmentmay be carried out. Specifically, the preliminary nitriding may becarried out by heating the alloy for production of a phosphor in anitrogen-containing atmosphere for a prescribed time in a prescribedtemperature region. By introducing such a primary nitriding step, itbecomes possible to control the reactivity between the alloy andnitrogen in the subsequent nitriding treatment, and it is possible toindustrially facilitate the production of the phosphor from the alloy.

Further, the nitriding treatment may be carried out repeatedly in aplurality of times, as the case requires. In such a case, the conditionsfor the first firing (primary firing) and the firing conditions for thesecond firing (secondary firing) and subsequent firings are as describedabove, respectively. The conditions for the second and subsequentfirings may be set to be the same or different from the conditions forthe primary firing. By applying the nitriding treatment to the phosphorraw material in such a manner, it is possible to obtain the phosphor ofthe present invention wherein a nitride or oxynitride is a matrix.

[2-4. Post Treatments]

In the production method of the present invention, in addition to theabove-described steps, other steps may be carried out as the caserequires. For example, after the above-described firing step, apulverization step, a cleaning step, a classification step, a surfacetreatment step, a drying step, etc. may be carried out, as the caserequires.

[2-4-1. Pulverization Step]

In the pulverization, a pulverizer such as a hammer mill, a roll mill, aball mill, a jet mill, a ribbon blender, a V-type blender or a Henschelmixer, or pulverization by means of a mortar and a muddler may, forexample, be used. At that time, in order to suppress destruction of theformed phosphor crystals and to proceed with treatment for the purposeof e.g. disintegrating secondary particles, it is preferred that into acontainer made of e.g. alumina, silicon nitride, ZrO₂ or glass, ballsmade of the same material as such or made of iron-core polyurethane areput, and ball mill treatment is carried out for from 10 minutes to 24hours. In such a case, a dispersing agent such as an alkali phosphate ofan organic acid or hexamethaphosphoric acid may be used in an amount offrom 0.05 wt % to 2 wt %.

[2-4-2. Cleaning Step]

The cleaning step may be carried out, for example, by water such asdeionized water, an organic solvent such as ethanol, or an alkalineaqueous solution such as aqueous ammonia. For the purpose of removing animpurity phase deposited on the surface of the phosphor, such as toremove the used flux, thereby to improve the emission properties, it isalso possible to use an acidic aqueous solution containing an inorganicacid such as hydrochloric acid, nitric acid, sulfuric acid, aquaregia ora mixture of hydrofluoric acid and sulfuric acid, or an organic acidsuch as acetic acid.

For the purpose of removing an amorphous content being an impurityphase, an acidic aqueous solution containing e.g. hydrofluoric acid,ammonium fluoride (NH₄F), ammonium hydrogen fluoride (NH₄HF₂), sodiumhydrogen fluoride or potassium hydrogen fluoride, may be used. Amongthem, a NH₄HF₂ aqueous solution is preferred. The concentration of theNH₄HF₂ aqueous solution is usually from 1 wt % to 30 wt %, preferablyfrom 5 wt % to 25 wt %. Further, as the case requires, these reagentsmay suitably be mixed for use.

Further, after the cleaning treatment with an alkaline aqueous solutionor an acidic aqueous solution, it is preferred to carry out furthercleaning with water. By such a cleaning step, it is possible to improvethe luminance, emission intensity, absorption efficiency and objectcolor of the phosphor.

In an example of the cleaning step, a fired product after cleaning isstirred for 1 hour in a 10 wt % NH₄HF₂ aqueous solution in an amount 10times by weight ratio, then dispersed in water and then left to standstill for 1 hours, so that cleaning is preferably carried out to such anextent that the pH of the supernatant will be neutral (about pH 5 to 9).If the above supernatant is deviated to basic or acidic, when it ismixed with the after-mentioned liquid medium or the like, it mayadversely affect the liquid medium or the like.

In order to remove an impurity formed during the acid cleaning,preferred is a method of carrying out cleaning with a second liquidafter cleaning with a first liquid, or a method of cleaning with aliquid having two or more substances mixed. As an example of the former,a process may be mentioned wherein cleaning with a NH₄HF₂ aqueoussolution is followed by cleaning with hydrochloric acid and finally bywashing with water. As an example of the latter, a process may bementioned wherein cleaning with a mixed aqueous solution of NH₄HF₂ andHNO₃, is followed by washing with water.

The degree of the above cleaning may be represented by an electricalconductivity of the supernatant obtained by dispersing the phosphorafter the cleaning in water 10 times by weight ratio, followed by beingleft to stand still for 1 hour. Such an electrical conductivity shouldbetter be low from the viewpoint of the emission properties, but whenalso the productivity is taken into consideration, it is preferred tocarry out the cleaning treatment repeatedly until it becomes usually atmost 10 mS/m, preferably at most 5 mS/m, more preferably at most 4 mS/m.

For the electrical conductivity, the phosphor is dispersed by stirringin water 10 times by weight for a prescribed time (e.g. 10 minutes),then left to stand still for 1 hour to let particles having heavierspecific gravity than water be naturally precipitated, whereupon theelectrical conductivity of the supernatant may be measured by means ofe.g. an electrical conductivity meter “EC METE CM-30G” manufactured byDKK-TOA Corporation. Water to be used for the cleaning treatment or themeasurement of the electrical conductivity is not particularly limited,but demineralized water or distilled water is preferred. One having lowelectrical conductivity is particularly preferred, and one having anelectrical conductivity of usually at least 0.0064 mS/m and usually atmost 1 mS/m, preferably at most 0.5 mS/m, is used. Here, the measurementof the electrical conductivity is carried out usually at roomtemperature (about 25° C.).

[2-4-3. Classification Step]

The classification step can be carried out, for example, by watersieving or by means of various classifiers such as various air flowclassifiers or shaking sieves. It is particularly preferred to employ adry system classification by means of nylon mesh, whereby it is possibleto obtain a phosphor having good dispersibility having a weight mediandiameter of about 10 μm.

Further, it is preferred to use the dry system classification by meansof nylon mesh and water sieving treatment in combination, whereby it ispossible to obtain a phosphor having good dispersibility having a weightmedian diameter of about 20 μm. Here, water sieving or water sievingtreatment is usually capable of dispersing phosphor particles at aconcentration of from 0.1 wt % to 10 wt % in an aqueous medium. Further,in order to suppress modification of the phosphor, the pH of the aqueousmedium is adjusted usually at least 4, preferably at least 5 and usuallyat most 9, preferably at most 8. Further, at the time of obtainingphosphor particles having the above-mentioned weight median diameter, inthe water sieving and hydraulic elutriation treatment, it is preferredto carry out the sieving treatment in two steps e.g. particles of atmost 50 μm are obtained, and then particles of at most 30 μm areobtained, from the viewpoint of the balance of the operation efficiencyand yield. Further, it is preferred to carry out sieving treatmentwherein the lower limit is usually at least 1 μm, preferably at least 5μm.

[2-4-4. Surface Treatment Step]

At the time of producing a light-emitting device by using the phosphorof the present invention, in order to further improve the weatherresistance such as moisture resistance or to improve the dispersibilityin a resin in the after-mentioned phosphor-containing portion of thelight-emitting device, surface treatment such as covering the surface ofthe phosphor with a different material, may be carried out as the caserequires.

The material which may be present on the surface of the phosphor(hereinafter sometimes referred to as “a surface treatment material”)may, for example, be an organic compound, an inorganic compound and aglass material.

The organic compound may, for example, be a heat meltable polymer suchas an acrylic resin, a polycarbonate, a polyamide or a polyethylene, alatex, or a polyorganosiloxane.

The inorganic compound may, for example, be a metal oxide such asmagnesium oxide, aluminum oxide, silicon oxide, titanium oxide,zirconium oxide, tin oxide, germanium oxide, tantalum oxide, niobiumoxide, vanadium oxide, boron oxide, antimony oxide, zinc oxide, yttriumoxide or bismuth oxide, a metal nitride such as silicon nitride oraluminum nitride, an orthophosphate such as calcium phosphate, bariumphosphate or strontium phosphate, a polyphosphate, or a combination of aphosphate of an alkali metal and/or alkaline earth metal with a calciumsalt such as a combination of sodium phosphate with calcium nitrate.

The glass material may, for example, be a borosilicate, a phoshosilicateor an alkali metal silicate. One of such surface treatment materials maybe used alone, or two or more of them may be used in an optionalcombination and ratio.

In the phosphor of the present invention obtainable by the above surfacetreatment, the presence of the surface treatment material isprerequisite, and the following may, for example, be mentioned as theembodiments. (i) An embodiment wherein the above surface treatmentmaterial constitutes a continuous film to cover the surface of thephosphor. (ii) An embodiment wherein the above surface treatmentmaterial is deposited on the surface of the phosphor in the form ofnumeral fine particles to cover the surface of the phosphor.

The deposition amount or covering amount of the surface treatmentmaterial on the surface of the phosphor is optional so long as theeffects of the present invention are not substantially thereby impaired,but it is usually at least 0.1 wt %, preferably at least 1 wt %, morepreferably at least 5 wt %, further preferably at least 10 wt % andusually at most 50 wt %, preferably at most 30 wt %, more preferably atmost 20 wt %, based on the weight of the phosphor. If the amount of thesurface treatment material is too much to the phosphor, the emissionproperties of the phosphor may be impaired, and if it is too little, thesurface coverage tends to be incomplete, and no improvement of themoisture resistance or dispersibility may be observed.

The film thickness (layer thickness) of the surface treatment materialto be formed by the surface treatment is optional so long as the effectsof the present invention are not substantially thereby impaired, but itis usually at least 10 nm, preferably at least 50 nm and usually at most2,000 nm, preferably at most 1,000 nm. If this film thickness of toothick, the emission properties of the phosphor may be impaired, and ifit is too thin, the surface coverage tends to be inadequate, and noimprovement of the moisture resistance or dispersibility may beobserved.

The method for the surface treatment is not particularly limited, andfor example, a coverage treatment method by the following metal oxide(silicon oxide) may be mentioned.

The phosphor of the present invention is mixed in an alcohol such asethanol and stirred, and further, an alkaline aqueous solution such asaqueous ammonia is mixed and stirred. Then, a hydrolyzable alkyl silicicacid ester such as tetraethylorthosilicic acid is mixed and stirred. Theobtained solution is left to stand for from 3 minutes to 60 minutes,whereupon the supernatant containing silicon oxide particles notdeposited on the surface of the phosphor, is removed by e.g. a dropper.Then, the mixing of an alcohol, stirring, being left to stand still andremoval of the supernatant, are repeated a few times, and then, via areduced pressure drying step at from 120° C. to 150° C. for from 10minutes to 5 hours, e.g. 2 hours, the surface treated phosphor isobtained.

As the method for surface treatment of the phosphor, a known method mayfurther be used, such as a method of depositing e.g. spherical siliconoxide fine powder on the phosphor (JP-A-2-209989, JP-A-2-233794), amethod of depositing a coating film of a silicon-type compound on thephosphor (JP-A-3-231987), a method of covering the surface of fineparticles of a phosphor with fine particles of a polymer(JP-A-6-314593), a method of coating a phosphor with an organicmaterial, an inorganic material and glass material, etc.(JP-A-2002-223008), a method of covering the surface of a phosphor by achemical vapor phase reaction method (JP-A-2005-82788), or a method ofdepositing particles of a metal compound (JP-A-2006-28458).

[3. Phosphor-Containing Composition]

The phosphor-containing composition of the present invention comprisesthe phosphor of the present invention and a liquid medium. In a casewhere the phosphor of the present invention is used for an applicationto e.g. a light-emitting device, it is preferred to use it in a formdispersed in a liquid medium i.e. in a form of a phosphor-containingcomposition.

As the liquid medium useful for the phosphor-containing composition ofthe present invention, an optional one may be selected for use dependingupon the purpose, so long as it shows a liquid nature under the desiredapplication conditions and so long as the phosphor of the presentinvention can suitably be dispersed therein, and no undesirable reactionor the like will take place. Examples of such a liquid medium include asilicone resin, an epoxy resin, a polyvinyl resin, a polyethylene resin,a polypropylene resin, a polyester resin, etc. One of such liquid mediamay be used alone, or two or more of them may be used in an optionalcombination and ratio. Further, an organic solvent may be incorporatedto the above liquid medium.

The amount of the liquid medium to be used may suitably be adjusteddepending upon the particularly application, but usually, it is within arange of usually at least 3 wt %, preferably at least 5 wt % and usuallyat most 30 wt %, preferably at most 15 wt %, by the weight ratio of theliquid medium to the phosphor of the present invention. If the liquidmedium is too little, the amount of luminescence from thephosphor-containing composition per volume tends to be low, and if it istoo much, the dispersibility of the phosphor powder tends to be poor,and color unevenness tends to occur.

The phosphor-containing composition of the present invention maycontain, in addition to the phosphor of the present invention and theliquid medium, other optional components depending upon the particularapplication, etc. As such other components, a diffusing agent, athickener, a filler, an interfering agent, etc. may be mentioned.Specifically, a silica type fine powder such as aerosol, alumina or thelike may be mentioned. One of such other components may be used alone,or two or more of them may be used in an optional combination and ratio.

In a case where the phosphor-containing composition is used as aconstituting component of a light-emitting device (e.g. theafter-descried second illuminant), the phosphor-containing compositioncan be made to be the above constituting component by curing the liquidmedium.

[4. Light-Emitting Device]

Now, the light-emitting device of the present invention will bedescribed. The light-emitting device of the present invention is alight-emitting device having a first illuminant and a second illuminantwhich emits visible light under irradiation with light from the firstilluminant, wherein as the second illuminant, a first phosphor iscontained, which contains at least one phosphor of the presentinvention.

[4-1. First Illuminant]

The first illuminant in the light-emitting device of the presentinvention is one which emits light to excite the after-described secondilluminant. The emission wavelength of the first illuminant is notparticularly limited so long as it is one which overlaps with theabsorption wavelength of the after-described second illuminant, andilluminants within a wide emission wavelength region can be used.Further, as the first illuminant to be suitably used, for example, onehaving an emission peak within a wavelength range of from 300 nm to 420nm, one having an emission peak within a wavelength range of from 420 to450 nm, or one having an emission peak within a wavelength range of from420 nm to 500 nm, may, for example, be mentioned.

Usually, an illuminant having an emission wavelength within a range offrom a near ultraviolet region to a blue color region is used, and as aspecific numerical value, an illuminant having an emission wavelength ofusually at least 300 nm, preferably at least 330 nm and usually at most500 nm, preferably at most 480 nm, is used.

As such a first illuminant, a semiconductor light-emitting element isusually employed. Specifically, a light-emitting diode (LED) or asemiconductor laser diode (hereinafter sometimes referred to simply as“LD”) may, for example, be used.

Among them, as the first illuminant, a GaN type LED or LD using a GaNtype compound semiconductor is preferred. Because, the GaN type LED orLD has a remarkably large emission output or external quantum efficiencyas compared with a SiC type LED or the like which emits light in thisregion, and by combining it with the above phosphor, it is possible toobtain very bright emission of light with a very low electric power. Forexample, to a current load of 20 mA, the GaN type LED or LD usually hasan emission intensity at a level of at least 100 times that of the SiCtype. In the GaN type LED or LD, one having an Al_(X)Ga_(Y)Nlight-emitting layer, a GaN light-emitting layer or an In_(X)Ga_(Y)Nlight-emitting layer is preferred. In the GaN type LED, one having anIn_(X)Ga_(Y)N light-emitting layer is particularly preferred among them,since the emission intensity is very high. In the GaN type LD, onehaving a multiple quantum well structure of an In_(X)Ga_(Y)N layer and aGaN layer is particularly preferred, since the emission intensity isvery high.

Here, in the above description, the value of X+Y is usually a valuewithin a range of from 0.8 to 1.2. In the GaN type LED, one having Zn orSi doped to such a light-emitting layer or one having no dopant ispreferred for adjustment of the emission properties.

The GaN type LED is one comprising such a light-emitting layer, ap-layer, a n-layer, electrodes and an substrate, as basic structuralelements, and one having a hetero structure wherein a light-emittinglayer is sandwiched between n-type and p-type Al_(X)Ga_(Y)N layers, GaNlayers or In_(X)Ga_(Y)N layers is preferred, since the luminousefficiency is high. Further, one having such a hetero structure madeinto a quantum well structure is more preferred, since the luminousefficiency is higher. Such LED or LD is already commercialized andreadily available.

[4-2. Second Illuminant]

The second illuminant in the light-emitting device of the presentinvention is an illuminant which emits visible light under irradiationwith light from the above-described first illuminant, and it contains afirst phosphor (the phosphor of the present invention) and at the sametime, may suitably contain a second phosphor depending upon theparticular application, etc. Further, the second illuminant is, forexample, constituted by dispersing the first and/or second phosphor in asealing material.

[4-2-1. First Phosphor]

In the light-emitting device of the present invention, the secondilluminant is one containing the above-described phosphor of the presentinvention, and contains, as a first phosphor, at least one phosphor ofthe present invention. Further, as the first phosphor, in addition tothe phosphor of the present invention, a phosphor which emitsfluorescence of the same color as the phosphor of the present invention(hereinafter sometimes referred to as “the same color concomitantphosphor”) may be used at the same time. Usually, the phosphor of thepresent invention is a yellow phosphor, and as the first phosphor,together with the phosphor of the present invention, another type ofyellow to orange phosphor (the same color concomitant phosphor) may beused in combination.

The same color concomitant phosphor may, for example, be Y₃Al₅O₁₂:Ce, orEu-activated M_(x) (Si, Al)₁₂(O, N)₁₆ (wherein M is a metal element suchas Ca or Y, and x is one obtained by dividing the number of moles of theoxygen atom by the average valency of M, and the number of moles of theoxygen atom is usually larger than 0 and at most 4.3). Here, one ofthese may be used alone, or two or more of them may be used in anoptional combination and ratio.

The emission peak wavelength λ_(p) (nm) of the same color concomitantphosphor is not particularly limited, but it is within a wavelengthrange of usually at least 500 nm, preferably at least 520 nm, andusually at most 650 nm, preferably at most 630 nm. If the emission peakwavelength of the first phosphor is too short or too long, it tends tobe difficult to obtain a good white color in the combination with thefirst illuminant or with the second phosphor.

The full width at half maximum (FWHM) of the emission peak of the samecolor concomitant phosphor is not limited, but it is usually at least110 nm, preferably at least 120 nm and usually at most 280 nm. If thisfull width at half maximum is too narrow, the color rendering propertyis likely to be low.

In a case where as the first phosphor, the phosphor of the presentinvention and another phosphor (the same color concomitant phosphor) areused, the ratio of the two is optional so long as the effects of thepresent invention are not substantially thereby impaired. However, theratio of the phosphor of the present invention should better be large.Specifically, the ratio of the phosphor of the present invention in theentire first phosphor is usually at least 40 wt %, preferably at least60 wt %, more preferably at least 70 wt %. However, it is particularlypreferred to use only the phosphor of the present invention as the firstphosphor.

[4-2-2. Second Phosphor]

The second illuminant in the light-emitting device of the presentinvention may contain, in addition to the above-described firstphosphor, another phosphor (i.e. a second phosphor). This secondphosphor is a phosphor having an emission wavelength different from thefirst phosphor. Usually, such a second phosphor is used to adjust theemission color of the second illuminant, and therefore, as the secondphosphor, a phosphor to emit fluorescence of a color different from thefirst phosphor, is used in many cases.

As mentioned above, as the first phosphor, the phosphor of the presentinvention is usually used, and therefore, as the second phosphor, it ispreferred to use, for example, a phosphor having an emission peak withina wavelength range of from 565 nm to 780 nm (hereinafter sometimesreferred to as “an orange or red phosphor”), a phosphor having anemission peak within a wavelength of from 420 nm to 500 nm (hereinaftersometimes referred to as “a blue phosphor”), or a phosphor having anemission peak within a wavelength range of from 500 nm to 550 nm(hereinafter sometimes referred to as “a green phosphor”).

Further, as the second phosphor, one phosphor may be used alone, or twoor more phosphors may be used in an optional combination and ratio.Further, the ratio of the second phosphor to the first phosphor is alsooptional unless the effects of the present invention are notsubstantially impaired. Accordingly, the amount of the second phosphorto be used as well as the combination of phosphors to be used as thesecond phosphor and their ratio may optionally be set depending upon theparticular application of the light-emitting device, etc. Now, thesecond phosphor will be described in further detail.

[4-2-2-1. Orange or Red Phosphor]

The emission peak wavelength of the orange or red phosphor is preferablywithin a wavelength range of usually at least 565 nm, preferably atleast 575 nm, more preferably at least 580 nm and usually at most 780nm, preferably at most 700 nm, more preferably at most 680 nm.

Such an orange or red phosphor may, for example, be a europium-activatedalkaline earth silicon nitride phosphor represented by(Mg,Ca,Sr,Ba)₂Si₅N₈:Eu, which is constituted by fractured particleshaving a red fracture surface and which emits light in a red colorregion, or a europium-activated rare earth oxychalcogenide phosphorrepresented by (Y,La,Gd,Lu)₂O₂S:Eu, which is constituted by grownparticles having substantially a spherical shape as a regularcrystal-growth shape and which emits light in a red color region.

The full width at half maximum of the emission peak of the red phosphoris usually within a range of from 1 nm to 100 nm. Further, the externalquantum efficiency is usually at least 60%, preferably at least 70%, andthe weight median diameter is usually at least 1 μm, preferably at least5 μm, further preferably at least 10 μm and usually at most 30 μm,preferably at most 20 μm, further preferably at most 15 μm.

Further, a phosphor containing an oxynitride and/or oxysulfidecontaining at least one element selected from the group consisting ofTi, Zr, Hf, Nb, Ta, W and Mo, as disclosed in JP-A-2004-300247, whichcontains an oxynitride having an α-SiAlON structure having a part or allof Al element substituted by Ga element, may also be used in the presentinvention.

Further, as the red phosphor, it is possible to use, for example, anEu-activated oxysulfide phosphor such as (La,Y)₂O₂S:Eu, an Eu-activatedoxide phosphor such as Y(V,P)O₄:Eu or Y₂O₃:Eu, Eu, Mn-activated silicatephosphor such as (Ba,Mg)₂SiO₄:Eu,Mn, or (Ba,Sr,Ca,Mg)₂SiO₄:Eu,Mn, anEu-activated tungstenate phosphor such as LiW₂O₈:Eu, LiW₂O₈:Eu,Sm,Eu₂W₂O₉, Eu₂W₂O₉:Nb, or Eu₂W₂O₉:Sm, an Eu-activated sulfide phosphorsuch as (Ca,Sr)S:Eu, an Eu-activated aluminate phosphor such asYAlO₃:Eu, an Eu-activated silicate phosphor such as Ca₂Y₈(SiO₄)₈O₂:Eu,LiY₉(SiO₄)₆O₂:Eu, (Sr,Ba,Ca)₃SiO₅:Eu, or Sr₂BaSiO₅:Eu, a Ce-activatedaluminate phosphor such as (Y,Gd)₃Al₅O₁₂:Ce, or (Tb,Gd)₃Al₅O₁₂:Ce, anEu-activated oxide, nitride or oxynitride phosphor such as(Mg,Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Mg,Ca,Sr,Ba)Si(N,O)₂:Eu, or(Mg,Ca,Sr,Ba)AlSi(N,O)₃:Eu, an Eu,Mn-activated halophosphate phosphorsuch as (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu,Mn, an Eu,Mn-activated silicatephosphor such as Ba₃MgSi₂O₈:Eu,Mn, or (Ba,Sr,Ca,Mg)₃(Zn,Mg)Si₂O₈:Eu,Mn,a Mn-activated germinate phosphor such as 3.5MgO.0.5MgF₂.GeO₂:Mn, anEu-activated oxynitride phosphor such as an Eu-activated α-SiAlON, anEu,Bi-activated oxide phosphor such as (Gd,Y,Lu,La)₂O₃:Eu,Bi, anEu,Bi-activated oxysulfie phosphor such as (Gd,Y,Lu,La)₂O₂S:Eu,Bi, anEu,Bi-activated vanadinate phosphor such as (Gd,Y,Lu,La)VO₄:Eu,Bi, anEu, Ce-activated sulfide phosphor such as SrY₂S₄:Eu, Ce, a Ce-activatedsulfide phosphor such as CaLa₂S₄:Ce, an Eu,Mn-activated phosphatephosphor such as (Ba,Sr,Ca)MgP₂O₇:Eu,Mn, or (Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu,Mn,an Eu,Mo-activated tungstate phosphor such as (Y,Lu)₂WO₆:Eu,Mo, an Eu,Ce-activated nitride phosphor such as (Ba,Sr,Ca)_(x)Si_(y)N_(z):Eu, Ce(wherein each of x, y and z is an integer of at least 1), anEu,Mn-activated halophosphate phosphor such as(Ca,Sr,Ba,Mg)₁₀(PO₄)₆(F,Cl,Br,OH):Eu,Mn, or a Ce-activated silicatephosphor such as((Y,Lu,Gd,Tb)_(1−x−y)Sc_(x)Ce_(y))₂(Ca,Mg)_(1−r)(Mg,Zn)_(2+r)Si_(z−q)Ge_(q)O_(12+δ).

As the red phosphor, it is also possible to use a red organic phosphormade of a rare earth element ion complex having, as a ligand, an anionsuch as a β-diketonate, a β-diketone, an aromatic carboxylic acid or aBrønsted acid, a perylene pigment (such asdibenzo{[f,f′]-4,4′,7,7′-tetraphenyl}diindeno[1,2,3-cd:1′,2′,3′-lm]perylene),an anthraquinone pigment, a lake pigment, an azo pigment, a quinacridonepigment, an anthracene pigment, an isoindoline pigment, an isoindolinonepigment, a phthalocyanine pigment, a triphenylmethane basic dye, anindanthrone pigment, an indophenol pigment, a cyanine pigment or adioxazine pigment.

Among the above, the red phosphor preferably contains(Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Ca,Sr,Ba)Si(N,O)₂:Eu, (Ca,Sr,Ba)AlSi(N,O)₃:Eu,(Ca,Sr,Ba)AlSi(N,O)₃:Ce, (Sr,Ba)₃SiO₅:Eu, (Ca,Sr)S:Eu, (La,Y)₂O₂S:Eu oran Eu complex. More preferably, it contains (Ca,Sr,Ba)₂Si₅(N,O)₈:Eu,(Ca,Sr,Ba)Si(N,O)₂:Eu, (Ca,Sr,Ba)AlSi(N,O)₃:Eu, (Ca,Sr,Ba)AlSi(N,O)₃:Ce,(Sr,Ba)₃SiO₅:Eu, (Ca,Sr)S:Eu or (La,Y)₂O₂S:Eu, or a β-diketone type Eucomplex such as an Eu (dibenzoylmethane)3.1,10-phenanthroline complex,or a carboxylic acid type Eu complex. Particularly preferred is(Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Sr,Ca)AlSi(N,O):Eu or (La,Y)₂O₂S:Eu.

Further, in the above exemplification, as the orange phosphor,(Sr,Ba)₃SiO₅:Eu is preferred. One of such orange or red phosphors may beused alone, or two or more of them may be used in an optionalcombination and ratio.

[4-2-2-2. Blue Phosphor]

The emission peak wavelength of the blue phosphor is preferably within arange of usually at least 420 nm, preferably at least 430 nm, morepreferably at least 440 nm and usually at most 500 nm, preferably atmost 480 nm, more preferably at most 470 nm, further preferably at most460 nm.

The full width at half maximum of the emission peak of the blue phosphoris usually within a range of from 20 nm to 80 nm. Further, the externalquantum efficiency is usually at least 60%, preferably at least 70%, andthe weight median diameter is usually at least 1 μm, preferably at least5 μm, further preferably at least 10 μm and usually at most 30 μm,preferably at most 20 μm, more preferably at most 15 μm.

Such a blue phosphor may, for example, be a europium-activated bariummagnesium aluminate phosphor represented by Ba,Sr, Ca)MgAl₁₀O₁₇:Euconstituted by grown particles having a substantially hexagonal shape asa regular crystal growth shape and which emits light in a blue region, aeuropium-activated calcium halophosphate phosphor represented by(Mg,Ca,Sr,Ba)₅(PO₄)₃(Cl,F):Eu which is constituted by grown particleshaving a substantially spherical shape as a regular crystal growth shapeand which emits light in a blue region, a europium-activated alkalineearth chloroborate phosphor represented by (Ca,Sr,Ba)₂B₅O₉Cl:Eu which isconstituted by grown particles having a substantially cubic shape as aregular crystal growth shape and which emits light in a blue region or aeuropium-activated alkaline earth aluminate phosphor represented by(Sr,Ca,Ba)Al₂O₄:Eu or (Sr,Ca,Ba)₄Al₁₄O₂₅:Eu, which is constituted byfractured particles having a fracture surface and which emits light in abluish green region.

Further, as the blue phosphor, it is possible to use a Sn-activatedphosphate phosphor such as Sr₂P₂O₇:Sn, an Eu-activated aluminatephosphor such as (Sr,Ca,Ba)Al₂O₄:Eu or (Sr,Ca,Ba)₄Al₁₄O₂₅:Eu,BaMgAl₁₀O₁₇:Eu, (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu, BaMgAl₁₀O₁₇:Eu, Tb,Sm,BaAl₈O₁₃:Eu, a Ce-activated thiogalate phosphor such as SrGa₂S₄:Ce, orCaGa₂S₄:Ce, an Eu,Mn-activated aluminate phosphor such as(Ba,Sr,Ca)MgAl₁₀O₁₇:Eu,Mn, an Eu-activated halophosphate phosphor suchas (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu, or(Ba,Sr,Ca)₅(PO₄)₃(Cl,F,Br,OH):Eu,Mn,Sb, an Eu-activated silicatephosphor such as BaAl₂Si₂O₈:Eu, or (Sr,Ba)₃MgSi₂O₈:Eu, an Eu-activatedphosphate phosphor such as Sr₂P₂O₇:Eu, a sulfide phosphor such asZnS:Ag, or ZnS:Ag,Al, a Ce-activated silicate phosphor such asY₂SiO₅:Ce, a tungstate phosphor such as CaWO₄, an Eu,Mn-activatedborophosphate phosphor such as (Ba,Sr,Ca)BPO₅:Eu,Mn,(Sr,Ca)₁₀(PO₄)₈.nB₂O₃:Eu, or 2SrO.0.84P₂O_(5.0.16)B₂O₃:Eu, anEu-activated halosilicate phosphor such as Sr₂Si₃O_(8.2)SrCl₂:Eu, anEu-activated oxynitride phosphor such as SrSi₉Al₁₉ON₃₁:Eu, orEuSi₉Al₁₉ON₃₁, or a Ce-activated oxynitride phosphor such asLa_(1−x)Ce_(x)Al(Si_(6−z)Al_(z))(N_(10−z)O_(z)) (wherein x and z arenumbers which satisfy 0≦x≦1 and 0≦z≦6, respectively),La_(1−x−y)Ce_(x)Ca_(y)Al(Si_(6−z)Al_(z))(N_(10−z)O_(z)) (wherein x, yand z are numbers which satisfy 0≦x≦1, 0≦y≦1 and 0≦z≦6, respectively),etc.

Further, as the blue phosphor, it is also possible to use a fluorescentpigment of a naphthalic acid imide type, benzoxazole type, styryl type,coumarin type, pyrazoline type or triazole type compound, or an organicphosphor such as a thulium complex.

In the above exemplification, the blue phosphor preferably contains(Ca,Sr,Ba)MgAl₁₀O₁₇:Eu, (Sr,Ca,Ba,Mg)₁₀(PO₄)₆(Cl,F)₂:Eu or(Ba,Ca,Mg,Sr)₂SiO₄:Eu. More preferably, it contains(Ca,Sr,Ba)MgAl₁₀O₁₇:Eu, (Sr,Ca,Ba,Mg)₁₀(PO₄)₈(Cl,F)₂:Eu or(Ba,Ca,Sr)₃MgSi₂O₈:Eu. Further preferably, it contains BaMgAl₁₀O₁₇:Eu,Sr₁₀(PO₄)₆(Cl,F)₂:Eu or Ba₃MgSi₂O₈:Eu. Further, among them, for lightingapplications and display applications, (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu or(Ca,Sr,Ba)MgAl₁₀O₁₇:Eu is particularly preferred. Further, one of suchblue phosphors may be used alone, or two or more of them may be used inan optional combination and ratio.

[4-2-2=3. Green Phosphor]

The emission peak wavelength of the green phosphor is preferably withina range of usually more than 500 nm, preferably at least 510 nm, morepreferably at least 515 nm and usually at most 550 nm, preferably atmost 540 nm, further preferably at most 535 nm. If this emission peakwavelength λp is too short, the color tends to be bluish, and if it istoo long, the color tends to be yellowish, and thus in either case, theproperties as green light may be deteriorated.

The full width at half maximum of the emission peak of the greenphosphor is usually within a range of from 40 nm to 80 nm. Further, theexternal quantum efficiency is usually at least 60%, preferably at least70%, and the weight median diameter is usually at least 1 μm, preferablyat least 5 μm, more preferably at least 10 μm and usually at most 30 μm,preferably at most 20 μm, more preferably at most 15 μm.

A specific example of the green phosphor may, for example, be aeuropium-activated alkaline earth silicon oxynitride phosphorrepresented by (Mg,Ca,Sr,Ba)Si₂O₂N₂:Eu which is constituted by fracturedparticles having a fracture surface and which emits light in a greenregion.

As other green phosphors, it is possible to use an Eu-activatedaluminate phosphor such as Sr₄Al₁₄O₂₅:Eu, or (Ba,Sr,Ca)Al₂O₄:Eu, anEu-activated silicate phosphor such as (Sr,Ba)Al₂Si₂O₈:Eu,(Ba,Mg)₂SiO₄:Eu, (Ba,Sr, Ca,Mg)₂SiO₄:Eu, (Ba,Sr,Ca)₂(Mg,Zn)Si₂O₇:Eu, or(Ba,Ca,Sr,Mg)₉(Sc,Y,Lu,Gd)₂(Si,Ge)₆O₂₄:Eu, a Ce,Tb-activated silicatephosphor such as Y₂SiO₅:Ce,Tb, an Eu-activated borophosphate phosphorsuch as Sr₂P₂O₇—Sr₂B₂O₅:Eu, an Eu-activated halosilicate phosphor suchas Sr₂Si₃O₅-2SrCl₂:Eu, a Mn-activated silica phosphor such asZn₂SiO₄:Mn, a Tb-activated aluminate phosphor such as CeMgAl₁₁O₁₉:Tb, orY₃Al₅O₁₂:Tb, a Tb-activated silica phosphor such as Ca₂Y₈(SiO₄)₆O₂:Tb,or La₃Ga₅SiO₁₄:Tb, an Eu,Tb,Sm-activated thiogalate phosphor such as(Sr,Ba,Ca)Ga₂S₄:Eu,Tb,Sm, a Ce-activated aluminate phosphor such asY₃(Al,Ga)₅O₁₂:Ce or (Y,Ga,Tb,La,Sm,Pr,Lu)₃(Al,Ga)₅O₁₂:Ce, a Ce-activatedsilicate phosphor such as Ca₃Sc₂Si₃O₁₂:Ce, orCa₃(Sc,Mg,Na,Li)₂Si₃O₁₂:Ce, a Ce-activated oxide phosphor such asCaSc₂O₄:Ce, an Eu-activated oxynitride phosphor such as an Eu-activatedβ-SiAlON, an Eu,Mn-activated aluminate phosphor such asBaMgAl₁₀O₁₇:Eu,Mn, an Eu-activated aluminate phosphor such asSrAl₂O₄:Eu, a Tb-activated oxysulfide phosphor such as (La,Gd,Y)₂O₂S:Tb,a Ce,Tb-activated phosphate phosphor such as LaPO₄:Ce,Tb, a sulfidephosphor such as ZnS:Cu,Al, or ZnS:Cu,Au,Al, a Ce,Tb-activated boratephosphor such as (Y,Ga,Lu,Sc,La)BO₃:Ce,Tb, Na₂Gd₂B₂O₇:Ce,Tb, or(Ba,Sr)₂(Ca,Mg,Zn)B₂O₅:K,Ce,Tb, an Eu,Mn-activated halosilicate phosphorsuch as Ca₅Mg(SiO₄)₄Cl₂:Eu,Mn, an Eu-activated thioaluminate phosphor orthiogalate phosphor such as (Sr,Ca,Ba)(Al,Ga,In)₂S₄:Eu, anEu,Mn-activated halosilicate phosphor such as(Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu,Mn, and an Eu-activated oxynitride phosphorsuch as M₃Si₆O₉N₄:Eu, M₃Si₆O₁₂N₂:Eu (wherein M is an alkaline earthmetal element).

Further, as the green phosphor, it is also possible to use apyridine-phthalimide condensation derivative, a fluorescent pigment suchas a benzoxazinone type, quinazolinone type, coumarin type,quinophthalone type or naphthalic acid imido type, or an organicphosphor such as a terbium complex. One of the above exemplified greenphosphors may be used alone, or two or more of them may be used in anoptional combination and ratio.

[4-2-3. Other Properties of First and Second Phosphors]

The weight median diameters of the first phosphor and the secondphosphor are optional so long as the effects of the present inventionare not substantially thereby impaired, but they are preferably within arange of usually at least 0.1 μm, preferably at least 0.5 μm and usuallyat most 30 μm, preferably at most 20 μm. If the weight median diametersare too small, the luminance tends to be deteriorated, and the phosphorparticles tend to be agglomerated. On the other hand, if the weightmedian diameters are too large, the coating unevenness or clogging ofthe dispenser tends to occur.

[4-3. Combination of First Illuminant and First Phosphor and SecondPhosphor]

In the light-emitting device of the present invention, use or non-use,or the type of the second phosphor (red phosphor, blue phosphor, greenphosphor, etc.) as described above, may suitably be selected dependingupon the particularly application of the light-emitting device. Forexample, in a case where the first phosphor is a yellow phosphor, whenthe light-emitting device of the present invention is to be constructedas a light-emitting device to emit a yellow color, only the firstphosphor may be used, and it is usually unnecessary to use the secondphosphor.

On the other hand, it is possible to construct the light-emitting deviceby suitably combining the first phosphor (yellow phosphor) and thesecond phosphor, as phosphors contained in the second illuminant, inorder to obtain tight having a desired color.

The following combinations (i) to (iv) may be mentioned as examples of apreferred combination of the first illuminant, the first phosphor andthe second phosphor in the case of constructing such a light-emittingdevice.

(i) As the first illuminant, a blue illuminant (such as short wavelengthblue LED) having an emission peak wavelength in a wavelength range offrom 420 nm to 450 nm is used, and as the first phosphor, a yellowphosphor (such as the phosphor of the present invention) is used. It isthereby possible to construct a light-emitting device which emits apseudo white color.(ii) As the first illuminant, a blue illuminant (such as blue LED)having an emission peak wavelength in a wavelength range of from 420 nmto 500 nm, is used; as the first phosphor, a yellow phosphor (such asthe phosphor of the present invention) is used; and as the secondphosphor, a red phosphor is used. It is thereby possible to construct alight-emitting device which emits a light bulb color.(iii) As the first illuminant, a near ultraviolet illuminant (such asnear ultraviolet LED) having an emission peak wavelength in a wavelengthrange of from 300 nm to 420 nm, is used; as the first phosphor, a yellowphosphor (such as the phosphor of the present invention) is used, and asthe second phosphor, a blue phosphor is used. It is thereby possible toconstruct a light-emitting device which emits a pseudo white color.(iv) As the first illuminant, a near ultraviolet illuminant (such asnear ultraviolet LED) having an emission peak wavelength in a wavelengthrange of from 300 nm to 420 nm, is used; as the first phosphor, a yellowphosphor (such as the phosphor of the present invention) is used; and asthe second phosphor, a blue phosphor, a green phosphor and a redphosphor are used. It is thereby possible to construct a light-emittingdevice which emits a light bulb color.

[4-4. Sealing Material]

In the light-emitting device of the present invention, the first and/orsecond phosphor is employed usually by dispersing and sealing it in aliquid medium being a sealing material, followed by curing by heat orlight. As the liquid medium, the same one as disclosed in the abovesection [3. Phosphor-containing composition] may be mentioned.

Further, the liquid medium may contain a metal element which can be ametal oxide having a high refractive index in order to adjust therefractive index of the sealing component. Si, Al, Zr, Ti, Y, NB, B,etc. may be mentioned as examples for the metal element which presents ametal oxide having a high refractive index. One of these metal elementsmay be used alone, or two or more of them may be used in an optionalcombination and ratio.

The form of such a metal element to be present is not particularlylimited so long as the transparency of the sealing component is notimpaired. For example, it may form a uniform glass layer as ametalloxane bond or may be present in the form of particles in thesealing component. When it is present in the form of particles, thestructure of the interior of the particles may be amorphous or a crystalstructure, but in order to present a high refractive index, it ispreferably a crystal structure. Further, its particle diameter isusually at most the emission wavelength of a semiconductorlight-emitting element, preferably at most 100 nm, more preferably atmost 50 nm, particularly preferably at most 30 nm, in order not toimpair the transparency of the sealing component. For example, by mixingparticles of silicon oxide, aluminum oxide, zirconium oxide, titaniumoxide, yttrium oxide, niobium oxide or the like to a silicone material,it is possible to let the above metal element be present in the form ofparticles in the sealing component.

The above liquid medium may further contain known additives such as adiffusing agent, a filler, a viscosity-controlling agent, an ultravioletabsorber, etc. One of such additives may be used alone, or two or moreof them may be used in an optional combination and ratio.

[4-5. Construction of Light-Emitting Device (Other)]

So long as the light-emitting device of the present invention comprisesthe above first illuminant and second illuminant, other constructionsare not particularly limited. However, the above first illuminant andsecond illuminant are usually disposed on a suitable frame. At thattime, the second illuminant is excited by the emission of the firstilluminant (i.e. the first and second phosphors are excited) to emitlight, and the arrangement is made so that the emission of this firstilluminant and/or the emission of the second illuminant is taken out. Insuch a case, the first phosphor and the second phosphor may notnecessarily be mixed in the same layer, and for example, phosphors maybe contained in separate layers for the respective emission colors ofthe phosphors, for example, such that a layer containing the secondphosphor is laminated on a layer containing the first phosphor.

In the light-emitting device of the present invention, in addition tothe above excitation light source (the first illuminant), the phosphor(the second phosphor) and the frame, another component may be used. Assuch an example, the above-mentioned sealing material may be mentioned.In addition to the purpose of dispersing the phosphor (the secondilluminant) in the light-emitting device, such a sealing material may beused for the purpose of bonding the excitation light source (the firstilluminant), the phosphor (the second illuminant) and the frame.

[4-6. Embodiments of Light-Emitting Device]

Now, the light-emitting device of the present invention will bedescribed in further detail with reference to a specific embodiment, butit should be understood that the light-emitting device of the presentinvention is by no means restricted to the following embodiment, and itmay be practiced by modifying it optionally within a range not to departfrom the gist of the present invention.

FIG. 1 shows a diagrammatical perspective view illustrating thepositional relation between the first illuminant to be an excitationlight source and the second illuminant constructed as aphosphor-containing portion having the phosphor, in one embodiment ofthe light-emitting device of the present invention. In FIG. 1, referencenumeral 1 represents a phosphor-containing portion (the secondilluminant), reference numeral 2 represents a surface-emitting GaN typeLD as an excitation light source (the first illuminant), and referencenumeral 3 represents a substrate. In order to make a mutually contractedstate, LD(2) and the phosphor-containing portion (the second illuminant)(1) may be prepared separately, and their surfaces may be bonded to eachother by an adhesive or other means, or on the light-emitting surface ofLD(2), the phosphor-containing portion (the second illuminant) may beformed as a film. Consequently, LD(2) and the phosphor-containingportion (the second illuminant) (1) can be made to be in contact witheach other.

By adopting such a construction of the device, it is possible to avoid aloss of light quantity such that light from the excitation light source(the first illuminant) is reflected at the film surface of thephosphor-containing portion (the second illuminant) and dischargedoutside, whereby the luminous efficiency of the entire device can bemade good.

FIG. 2( a) is a diagrammatical cross-sectional view illustrating anembodiment of the light-emitting device having an excitation lightsource (the first illuminant) and a phosphor-containing portion (thesecond illuminant), which is a typical example of a light-emittingdevice in the form which is commonly called a shell form. In thelight-emitting device (4), reference numeral 5 represents a mount lead,reference numeral 6 an inner lead, reference numeral 7 an excitationlight source (the first illuminant), reference numeral 8 aphosphor-containing resin portion, reference numeral 9 a conductivewire, and reference numeral 10 a molded component.

FIG. 2( b) is a diagrammatical cross-sectional view illustrating oneembodiment of the light-emitting device having an excitation lightsource (the first illuminant) and a phosphor-containing portion (thesecond illuminant), which is a typical example of a light-emittingdevice in the form which is called a surface-mounting type. In the Fig.,reference numeral 22 represents an excitation light source (the firstilluminant), reference numeral 23 a phosphor-containing resin portion asthe phosphor-containing portion (the second illuminant), referencenumeral 24 a frame, reference numeral 25 a conductive wire, andreference numerals 26 and 27 electrodes.

[4-7. Uses of Light-Emitting Device]

Uses of the light-emitting device of the present invention are notparticularly limited, and it is useful in various fields wherein usuallight-emitting devices are employed. However, it is particularlysuitably employed as a light source for a lighting system or an imagedisplay device, since its color reproduction range is wide and the colorrendering properties are high.

[5. Lighting System]

The lighting system of the present invention is one provided with thelight-emitting device of the present invention. In a case where thelight-emitting device of the present invention is applied to thelighting system, the above-described light-emitting device may besuitably incorporated to a known lighting system. For example, as shownin FIG. 3, a surface-emitting lighting system (11) may be mentionedwherein the above-described light-emitting device (4) is incorporated.

FIG. 3 is a diagrammatical cross-sectional view illustrating anembodiment of the lighting system of the present invention. As shown inthis FIG. 3, the surface-emitting lighting system is such that on thebottom surface of a rectangular casing (12) having the inner surfacemade opaque with e.g. a white smooth surface, many light-emittingdevices (13) (corresponding to the above-described light-emitting device(4)) are disposed, while a light source, a circuit, etc. (not shown) todrive the light-emitting devices (13) are provided outside thelight-emitting devices, and to make the emission uniform, a diffusepanel (14) made of e.g. a milky white acrylic plate, is fixed at theportion corresponding to a cover of the casing (12).

And, by driving the surface-emitting lighting system (11) to apply avoltage to the excitation light source (the first illuminant) of thelight-emitting devices (13) to have light emitted, and a part of theemitted light is absorbed by the phosphor in the phosphor-containingresin portion as the phosphor-containing portion (the second illuminant)to have a visible light emitted, while by color mixing with blue light,etc. not absorbed by the phosphor, an emission having high colorrendering properties can be obtained, and this light is transmittedthrough the diffuser panel (14) and emitted upwards in the drawing,whereby illumination light having a uniform brightness will be obtainedin the plane of the diffuser panel (14) of the casing (12).

[6. Image Display Device]

The image display device of the present invention is one provided withthe light-emitting device of the present invention. In a case where thelight-emitting device of the present invention is used as a light sourcefor an image display device, there is no particularly limitation to thespecific construction of the image display device, but it is preferablyused together with a color filter. For example, in a case where theimage display device is a color image display device utilizing a colorliquid crystal display element, it is possible to form an image displaydevice by using the above-described light-emitting device as a backlightand combining an optical shutter utilizing liquid crystal with colorfilters having red, green and blue pixels.

The color reproduction range by light after passing through the colorfilters at that time, is, by NTSC ratio, usually at least 60%,preferably at least 80%, more preferably at least 90%, furtherpreferably at least 100%, and usually at most 150%. Further, the amountof transmitted light from each color filter (light use efficiency) tothe amount of transmitted light from the entire color filters is usuallyat least 20%, preferably at least 25%, more preferably at least 28%,further preferably at least 30%. The light use efficiency should betterbe high, but as three filters of red, green and blue are used, it isusually at most 33%.

EXAMPLES

Now, the present invention will be described in further detail withreference to Examples and Comparative Examples, but it should beunderstood that the present invention is by no means restricted to thefollowing Examples, and may be practiced by making optional changeswithin a range not to depart from the gist of the present invention.Here, measurement of emission properties, etc. of phosphors in Examplesand Comparative Examples were carried out by the following methods.

[Measuring Methods]

[Emission Spectrum]

The emission spectrum was measured by means of a fluorescence measuringapparatus (manufactured by JASCO Corporation) provided with a 150 Wxenon lamp as an excitation light source and a multichannel CCD detectorC7041 (manufactured by Hamamatsu Photonics) as a spectrum-measuringdevice. Light from the excitation light source was passed through adiffraction grating spectroscope having a focal distance of 10 cm, andonly excitation light having a wavelength of 460 nm was radiated to thephosphor via an optical fiber. Light generated from the phosphor underirradiation with the excitation light was spectrally divided by adiffraction grating spectroscope having a focal distance of 25 cm,whereby emission intensities at various wavelengths were measured by thespectrum measuring apparatus within the wavelength range of from 300 nmto 800 nm, and via signal treatments such as sensitivity correction by apersonal computer, an emission spectrum was obtained. Here, at the timeof the measurement, the measurement was carried out by setting the slitwidth of the light-receiving side spectroscope to be 1 nm.

[Chromaticity Coordinates]

The chromaticity coordinates of x, y color system (CIE 1931 colorsystem) were calculated as chromaticity coordinates x and y in the XYZcolor system as stipulated in JIS Z8701 by a method in accordance withJIS 28724 from the data in the wavelength region of from 420 nm to 800nm of the emission spectrum obtained by the above-described method.

[Absorption Efficiency]

The absorption efficiency α_(q) of a phosphor was obtained as follows.Firstly, a phosphor sample to be measured was made to have its surfacesufficiently smooth so that the measurement accuracy was maintained andpacked into a cell, which was attached to an integrating sphere.

To this integrating sphere, light was introduced by means of an opticalfiber from an emission light source (150 W Xe lamp) to excite thephosphor. The emission peak wavelength of light from the above emissionlight source was adjusted by means of e.g. a monochrometer (diffractiongrating spectroscope) to be a monochromatic light of 455 nm. Such amonochromatic light was radiated as an excitation light to the phosphorsample to be measured, and by means of a spectroscopic apparatus(MCPD7000 manufactured by Otsuka Electronics Co., Ltd.), the emission(fluorescence) of the phosphor sample and the spectrum with respect tothe reflected light, were measured. The light in the integrating spherewas led to a spectroscopic apparatus by means of an optical fiber.

The absorption efficiency α_(q) is a value obtained by dividing thephoton number N_(abs) of the excitation light absorbed by the phosphorsample, by the total photon number N of the excitation light.

The latter total photon number N of the excitation light is proportionalto the numerical value obtained by the following formula (Formula a).Therefore, as a reflector having a reflectance R of substantially 100%to the excitation light, “Spectralon” manufactured by Labsphere (havinga reflectance R of 98.8% to a light source of 455 nm) was attached, asan object to be measured, to the above-mentioned integrating sphere inthe same disposition as the phosphor sample and irradiated with anexcitation light, whereby the reflection spectrum I_(ref)(λ) wasmeasured by a spectroscopic apparatus, and the value of the followingformula (Formula a) was obtained.

$\begin{matrix}{\frac{1}{R}{\int{{\lambda \cdot {I_{ref}(\lambda)}}{\lambda}}}} & {{Formula}\mspace{14mu} a}\end{matrix}$

Here, the integral interval was set to be from 410 nm to 480 nm to anexcitation wavelength of 455 nm. The photon number N_(abs) of theexcitation light absorbed by the phosphor sample is proportional to theamount obtained by the following formula (Formula b).

$\begin{matrix}{{\frac{1}{R}{\int{{\lambda \cdot {I_{ref}(\lambda)}}{\lambda}}}} - {\int{{\lambda \cdot {I(\lambda)}}{\lambda}}}} & {{Formula}\mspace{14mu} b}\end{matrix}$

Therefore, the reflection spectrum I (λ) was obtained when thereflection sample as the object to obtain the absorption efficiencyα_(q) was attached. The integration range of the Formula b was set to bethe same as the integration range set for the Formula a. The actualmeasured value of spectrum is usually obtained as digital data dividedinto finite band widths relating to λ, and accordingly, the integrationsof the Formula a and the Formula b were obtained by summation based onthe band widths. Thus, α_(q)=N_(abx)/N=(Formula b)/(Formula a) wascalculated. Here, the reflectance was obtained by using light with awavelength of 780 nm whereby in the phosphor, substantially noabsorption or emission takes place.

[Object Color]

The measurement of the object color was carried out by means of colordifference meter CR300 manufactured MINOLTA using D65 as the standardlight. A sample was packed in a circular cell and its surface wasflattened, and the measurement was carried out by pressing the flattenedsurface to the measuring portion of the color difference meter.

[Carbon Content, Oxygen Content]

A sample was put in an impulse furnace, and oxygen and carbon wereextracted by heating, whereupon the oxygen content concentration and thecarbon content concentration were determined by nondispersive infrareddetection.

[SEM-EDX]

The elemental composition of apart of phosphor particles, e.g. thecomposition of Gd, Y, etc., was analyzed by SEM-EDX (Scanning ElectronMicroscope-Energy Dispersive X-ray spectrometer) (S-3400N manufacturedby Hitachi, Ltd.)

Example 1 Production of Alloy

Respective metal raw materials of Ca solid metal blank, La solid metalblank, Ce solid metal blank and Si solid metal blank, were weighed sothat the compositional ratio of metal elements would beCa:La:Ce:Si=0.45:2.5:0.1:6 (molar ratio) and melted by a high frequencymeting furnaces to obtain an alloy. Then, the alloy was pulverized by ajet mill to obtain an alloy powder a having a median diameter of 4.3 μm.

Firing of Raw Material

In a glove box containing nitrogen as an operation atmosphere, 1 g ofthe alloy powder, 0.06 g of MgF₂ (6 wt % to the alloy material) and 0.08g of CeF₃ (8 wt % to the alloy material) were mixed in an aluminamortar, and the mixture was spread on a molybdenum tray having adiameter of 30 mm and set in an electric furnace with a molybdenum innerwall having a tungsten heater. After vacuuming from room temperature to120° C., 4% hydrogen-containing nitrogen gas was introduced to ordinarypressure, and while maintaining the supply rate of 0.5 L/min, thetemperature was raised to 800° C. and then raised from 800 to 1,550° C.at a rate of 0.5° C./min, followed by firing at 1,550° C. for 15 hours,whereupon the fired product was pulverized in an alumina mortar.

Treatment of Fired Product

The obtained fired product was pulverized in an agate mortar, and theobtained powder was stirred and cleaned with a NH₄HF₂ aqueous solutionhaving a concentration of 10 wt % for 1 hour, followed by washing withwater and drying to obtain a phosphor. The firing conditions, etc. ofthis phosphor and the results of property evaluations (the emissionproperties, absorption efficiency and object color) are shown inTable 1. Here, in Table 1, the luminance (%) and the emission intensity(%) are relative values to a YAG commercial product (P46-Y3 manufacturedby Kasei Optonix) being 100%. The phosphor in Example 1 had a luminanceas high as 119% to P46-Y3; a* and b* representing the object color were−14 and 88, respectively; the chroma (a*²+b*²)^(1/2) was very high at89; and the absorption efficiency was very high at 92%.

Example 2

A phosphor was obtained in the same manner as in Example 1 except thatthe cleaning with the ammonium hydrogen fluoride (NH₄HF₂) aqueoussolution was not carried out, and evaluations of its properties werecarried out. The firing conditions, etc. of this phosphor and theevaluation results of the properties are shown in Table 1. The phosphorin Example 2 had a luminance of 106% to P46-Y3; a* and b* representingthe object color were −11 and 83, respectively; the chroma(a*²+b*²)^(1/2) was 84; and the absorption efficiency was 92%. WhenExample 2 is compared with Example 1, the absorption efficiency wasequal, but Example 1 was superior with respect to other values, thusindicating that the effects of cleaning with the NH₄HF₂ aqueous solutionare distinct.

Example 3

A phosphor was obtained in the same manner as in Example 1 except thatthe amount of CeF₃ added was 6 wt %, and evaluations of its propertieswere carried out. The firing conditions, etc. of this phosphor and theevaluation results of the properties are shown in Table 1.

The content concentration of carbon in the phosphor obtained in Example3 was 0.03 wt %. The carbon content concentration in the raw materialalloy of this phosphor was 0.3 wt %, and the oxygen contentconcentration was 0.6 wt %. This indicates that by the firing in 4%hydrogen-containing nitrogen gas, the carbon content in the phosphor wasreduced to 0.03 wt %. That is, it is evident that in this Example, thefiring in the hydrogen-containing nitrogen atmosphere finallycontributed to reduction of the amount of carbon in the phosphor, and asa result, an extremely high luminance was obtained. Thus, according tothe method of the present invention, it is possible to obtain a phosphorhaving high luminance by using an alloy produced by using a graphitecrucible. This sample in Example 3 was further subjected to cleaningwith 1N hydrochloric acid, and then, the same chemical analysis as inExample A1 was carried out, whereby the chemical formula of the phosphorobtained was found to be Ca_(0.04)La_(2.7)Ce_(0.30)Si₆O₁₁O_(0.26).

Example 4

A phosphor was obtained in the same manner as in Example 3 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 3 and Example 4 are compared, it isevident that the effects for improving the luminance and emissionintensity, of the cleaning with the NH₄HF₂ aqueous solution, aredistinct.

Example 5

A phosphor was obtained in the same manner as in Example 1 except thatthe amount of CeF₃ was changed to 4 wt %, and evaluations of itsproperties were carried out. The firing conditions, etc. of thisphosphor and the evaluation results of the properties are shown in Table1.

Example 6

A phosphor was obtained in the same manner as in Example 5 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 5 and Example 6 are compared, it isevident that by the cleaning with the NH₄HF₂ aqueous solution, theluminance and the absorption efficiency are improved.

Example 7

A phosphor was obtained in the same manner as in Example 1 except thatthe amount of CeF₃ was changed to 2 wt %, and evaluations of itsproperties were carried out. The firing conditions, etc. of thisphosphor and the evaluation results of the properties are shown in Table1.

Example 8

A phosphor was obtained in the same manner as in Example 7 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 7 and Example 8 are compared, it isevident that the effects for improving the luminance and emissionintensity, of the cleaning with the NH₄HF₂ aqueous solution, aredistinct.

Example 9

A phosphor was obtained in the same manner as in Example 1 except that6% of only MgF₂ was added, and CeF₃ was not added, and evaluations ofits properties were carried out. The firing conditions, etc. of thisphosphor and the evaluation results of the properties are shown in Table1.

Comparative Example 1

A phosphor was obtained in the same manner as in Example 9 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 9 and Comparative Example 1 are compared,it is evident that by the cleaning with the NH₄HF₂ aqueous solution, theluminance, emission intensity and object color are improved.

Example 10

A phosphor was obtained in the same manner as in Example 1 except MgF₂was 6%, CeF₃ was 6%, LaF₃ was 2%, and the heating retention time was 40hours, and evaluations of its properties were carried out. The firingconditions, etc. of this phosphor and the evaluation results of theproperties are shown in Table 1. The phosphor in Example 10 had aluminance of 118% to P46-Y3; a* and b* representing the object colorwere −13 and 89, respectively; the chroma (a*²+b*²)^(1/2) was high at90; and the absorption efficiency showed a high value of 93%.

Example 11

A phosphor was obtained in the same manner as in Example 10 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. The phosphor in Example 11 had a luminance as high as97% to P46-Y3; a* and b* representing the object color were −10 and 79,respectively; the chroma (a*²+b*²)^(1/2) was high at 80; and theabsorption efficiency showed a high value of 94%. When Example 11 iscompared with Example 10, the absorption efficiency is substantiallyequal, but Example 10 is superior with respect to other values, wherebyit is evident that the effects of cleaning with the NH₄HF₂ aqueoussolution are distinct.

Example 12

A phosphor was obtained in the same manner as in Example 10 except thatthe type and blend amount of the flux were as shown in Table 1, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1.

Example 13

A phosphor was obtained in the same manner as in Example 12 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 12 and Example 13 are compared, it isevident that the effects for improving the luminance, of the cleaningwith the NH₄HF₂ aqueous solution, are distinct.

Example 14

A phosphor was obtained in the same manner as in Example 10 except thatthe type and blend amount of the flux were as shown in Table 1, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1.

Example 15

A phosphor was obtained in the same manner as in Example 14 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 14 and Example 15 are compared, it isevident that the effects for improving the luminance, of the cleaningwith the NH₄HF₂ aqueous solution, are distinct.

Example 16

A phosphor was obtained in the same manner as in Example 10 except thatthe type and blend amount of the flux were as shown in Table 1, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1.

Example 17

A phosphor was obtained in the same manner as in Example 16 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 16 and Example 17 are compared, it isevident that by the cleaning with the NH₄HF₂ aqueous solution, theluminance and object color are improved.

Example 18

A phosphor was obtained in the same manner as in Example 16 except CeF₃was not added, and evaluations of its properties were carried out. Thefiring conditions, etc. of this phosphor and the evaluation results ofthe properties are shown in Table 1.

Comparative Example 2

A phosphor was obtained in the same manner as in Example 18 except thatthe cleaning with the NH₄HF₂ aqueous solution was not carried out, andevaluations of its properties were carried out. The firing conditions,etc. of this phosphor and the evaluation results of the properties areshown in Table 1. When Example 18 and Comparative Example 2 arecompared, it is evident that by the cleaning with the NH₄HF₂ aqueoussolution, the luminance, absorption efficiency and object color areimproved.

TABLE 1 Ex. or Firing conditions Comp. First flux Second flux Third fluxFiring Ex. Amount Amount Amount time Cleaning No. Type (%) Type (%) Type(%) (hr) with acid Ex. 1 MgF₂ 6 CeF₃ 8 — — 15 Yes Ex. 2 MgF₂ 6 CeF₃ 8 —— 15 No Ex. 3 MgF₂ 6 CeF₃ 6 — — 15 Yes Ex. 4 MgF₂ 6 CeF₃ 6 — — 15 No Ex.5 MgF₂ 6 CeF₃ 4 — — 15 Yes Ex. 6 MgF₂ 6 CeF₃ 4 — — 15 No Ex. 7 MgF₂ 6CeF₃ 2 — — 15 Yes Ex. 8 MgF₂ 6 CeF₃ 2 — — 15 No Ex. 9 MgF₂ 6 CeF₃ 0 — —15 Yes Comp. MgF₂ 6 CeF₃ 0 — — 15 No Ex. 1 Ex. 10 MgF₂ 6 CeF₃ 6 LaF₃ 240 Yes Ex. 11 MgF₂ 6 CeF₃ 6 LaF₃ 2 40 No Ex. 12 MgF₂ 6 CeF₃ 8 — — 40 YesEx. 13 MgF₂ 6 CeF₃ 8 — — 40 No Ex. 14 MgF₂ 6 CeF₃ 10 — — 40 Yes Ex. 15MgF₂ 6 CeF₃ 10 — — 40 No Ex. 16 MgF₂ 6 CeF₃ 6 — — 40 Yes Ex. 17 MgF₂ 6CeF₃ 6 — — 40 No Ex. 18 MgF₂ 6 CeF₃ 0 — — 40 Yes Comp. MgF₂ 6 CeF₃ 0 — —40 No Ex. 2 Ex. or Evaluation results of properties Comp. Emissionproperties (455 nm excitation) Absorption Object color Ex. Emission peakChromaticity Chromaticity Luminance Emission efficiency LuminosityChroma No. wavelength (nm) coordinate x coordinate y (%) intensity (%)(%) L* a* b* (a*² + b*²)^(0.5) Ex. 1 540 0.441 0.539 119 119 92 96 −1488 89 Ex. 2 542 0.444 0.537 106 107 92 92 −11 83 84 Ex. 3 540 0.4400.540 115 115 — — — — — Ex. 4 540 0.441 0.539 101 103 — — — — — Ex. 5542 0.442 0.539 117 117 92 — — — — Ex. 6 542 0.440 0.540 102 105 88 — —— — Ex. 7 540 0.441 0.539 117 117 — — — — — Ex. 8 540 0.440 0.540 99 101— — — — — Ex. 9 540 0.430 0.545 105 105 84 95 −16 75 76 Comp. 537 0.4290.545 94 96 84 94 −14 64 66 Ex. 1 Ex. 10 540 0.438 0.542 118 120 93 95−13 89 90 Ex. 11 539 0.439 0.541 97 98 94 86 −10 79 80 Ex. 12 540 0.4410.540 117 120 92 — — — — Ex. 13 538 0.442 0.539 98 100 94 — — — — Ex. 14541 0.441 0.540 116 117 94 — — — — Ex. 15 542 0.444 0.538 97 98 93 — — —— Ex. 16 541 0.440 0.541 113 115 94 95 −13 90 91 Ex. 17 540 0.440 0.54094 95 93 86 −10 78 79 Ex. 18 537 0.426 0.549 108 110 92 93 −16 79 81Comp. 534 0.426 0.548 85 86 88 88 −12 65 66 Ex. 2 Notes) — : Nil or notmeasured. Washing with acid: After the firing, washing for 1 hour with a10% NH₄HF₂ aqueous solution. Luminance (%): Relative value to luminanceof YAG commercial product (P46-Y3) being 100%. Emission intensity (%):Relative value to emission intensity of YAG commercial product (P46-Y3)being 100%.

Comparative Example 3

CaSiN₂, LaN, CeO₂ and Si₃N₄ (manufactured by Denki Kagaku KogyoKabushiki Kaisha, average particle diameter: 0.5 μm, oxygen content:0.93 wt %, α-type content: 92%) were weighed as raw materials, and in acrucible made of boron nitride, 1.7 g of the raw material mixture wasfired at 2,000° C. under a nitrogen pressure of 0.92 MPa to obtain aphosphor. Here, the charged amounts of the respective raw materials, thefiring conditions, etc. are the same as in Example 8 inJP-A-2008-285659. The charged amounts and the firing conditions, etc.are shown in Table 2. Further, the evaluation results of the propertiesof the obtained phosphor (emission properties, absorption efficiency andobject color) are shown in Table 3.

TABLE 2 Charged amounts of the respective Charged amount Firing Comp.raw materials (g) (molar ratio) temp. Ex. No. CaSiN₂ LaN CeO₂ Si₃N₄ CaLa Ce (° C.) Comp. 0.546 0.642 0.044 0.467 2.2 1.6 0.10 2000 Ex. 3 Note)Charged amounts (molar ratio): Molar ratio of each element to 6 mol ofSi charged.

TABLE 3 Emission properties (460 nm excitation) Emission Emission peakAbsorption Object color Comp. Ex. intensity wavelength ChromaticityChromaticity efficiency Luminosity Chroma No. (%) (nm) coordinate xcoordinate y (%) L* a* b* (a*² + b*²)^(0.5) Comp. 49 591 0.519 0.473 8585 8 59 59 Ex. 3 Note) Emission intensity (%): Relative value toluminance of YAG commercial product (P46-Y3) being 100%.

Of the phosphor in Comparative Example 3, a* and b* representing theobject color were 8 and 59, respectively; the chroma (a*²+b*²)^(1/2) wasas low as 59; and the absorption efficiency showed a relatively lowvalue of 85%. From such results, it is evident that the phosphors of thepresent invention in Examples 1 to 18 have higher luminance than thephosphor in Comparative Example 3 (Example 8 in JP-A-2008-285659) andhave high chroma and high absorption efficiency and different values a*and b* for object color.

Comparative Example 4

CaSiN₂ powder, α-Si₃N₄ powder, LaN powder and La₄CeSi₁₀ alloy powderwere mixed in weight ratios of 0.352, 0.975. 1.574 and 0.468,respectively. About 0.7 g of the mixture was charged into a cruciblemade of boron nitride and fired (primary firing) at 2,000° C. under anitrogen pressure of 0.92 MPa, followed by secondary firing in thepresence of MgF₂ flux to obtain a phosphor. The raw materials, chargedamounts, firing conditions, etc. in this Comparative Example 4 are thesame as in Example II-6 in WO2008-132954. The charged raw materials forthe phosphor and the firing conditions, etc. in Comparative Example 4are shown in Table 4. Further, the evaluation results of properties ofthe obtained phosphor (emission properties, absorption efficiency andobject color) are shown in Table 5.

Comparative Example 5

CaSiN₂ powder, β-Si₃N₄ powder, LaN powder and La₄CeSi₁₀ alloy powderwere mixed in weight ratios of 0:261, 0.723, 1.168 and 0.347,respectively. About 1.2 g of the mixture was charged into a cruciblemade of boron nitride and fired (primary firing) at 2,000° C. under anitrogen pressure of 0.92 MPa, followed by secondary firing in thepresence of MgF₂ flux to obtain a phosphor. The charged raw materialsfor the phosphor and the firing conditions, etc. in Comparative Example5 are shown in Table 4. Further, the evaluation results of theproperties of the obtained phosphor (emission properties, absorptionefficiency and object color) are shown in Table 5.

TABLE 4 Primary firing conditions Second firing conditions Firing FiringComp. Charged raw Pressure temperature × Pressure temperature × Ex. No.materials Atmosphere (Pa) time Flux Atmosphere (Pa) time Comp. La₄CeSi₁₀N2 0.92 1,580° C. × 57 hr + MgF₂ N2 0.92 1,580° C. × 6 hr Ex. 4 alloy +LaN + α- 2,000° C. × 0.08 hr 0.9 wt % Si₃N₄ + CaSiN₂ Comp. La₄CeSi₁₀ N20.92 1,580° C. × 57 hr + MgF₂ N2 0.92 1,580° C. × 6 hr Ex. 5 alloy +LaN + β 2,000° C. × 0.08 hr 0.9 wt % Si₃N₄ + CaSiN₂

TABLE 5 Emission properties (460 nm excitation) Emission Emission peakAbsorption Object color Comp. Ex. intensity wavelength ChromaticityChromaticity efficiency Luminosity Chroma No. (%) (nm) coordinate xcoordinate y (%) L* a* b* (a*² + b*²)^(0.5) Comp. Ex. 4 76 564 0.4570.520 83 94 −8 62 62 Comp. Ex. 5 78 561 — — 87 94 −7 70 71 Note)Emission intensity (%): Relative value to luminance of YAG commercialproduct (P46-Y3) being 100%.

Of the phosphors in Comparative Examples 4 and 5, a* and b* representingthe object color were −8 and −7, and 62 and 70, respectively; the chroma(a*²+b*²)^(1/2) was as low as 62 and 71, respectively; and theabsorption efficiency showed relatively low values of 83 and 87%,respectively.

From such results, it is evident that the phosphors of the presentinvention in Examples 1 to 18 have higher luminance than the phosphordisclosed in Example in WO2008-132954, have high chroma and highabsorption efficiency, and have different values a* and b* of objectcolor.

Example 19 Low Temperature Raise in Alloy-Nitriding Temperature Region

A phosphor was obtained by firing under the same conditions as inExample 9 except that in Example 9, only in the temperature region offrom 1,250 to 1,350° C., the temperature raising rate was changed from0.5° C./min to 0.1° C./min. The evaluation results of the properties ofthis phosphor (emission properties, absorption efficiency and objectcolor) are shown in Table 6. Further, the evaluation results of thephosphor in Example 9 are shown for the purpose of comparison in Table6.

TABLE 6 Emission properties (455 nm excitation) Emission peak EmissionAbsorption Object color Comp. wavelength Chromaticity ChromaticityLuminance intensity efficiency Luminosity Chroma Ex. No. (nm) coordinatex coordinate y (%) (%) (%) L* a* b* (a*² + b*²)^(0.5) Ex. 19 540 0.4350.543 112 114 92 94 −16 87 88 Ex. 9 540 0.430 0.545 105 105 84 95 −16 7677 Note) Luminance (%): Relative value to luminance of YAG commercialproduct (P46-Y3) being 100%. Emission intensity (%): Relative value toluminance of YAG commercial product (P46-Y3) being 100%.

The phosphor in Example 19 had a luminance of 112% to P46-Y3, which washigher than the luminance of 105% in Example 9. This temperature rangecorresponds to the portion of from rising to termination of the heatgeneration peak during the nitriding reaction of the raw material alloy.It was found that by reducing the temperature raising rate in thistemperature range, it is possible to improve the luminance.

Examples 20 and 21 Alloy Composition

An experiment was carried out under the same conditions as in Example 19except that in Example 19, the flux was changed to 6 wt % of MgF₂, 6 wt% of CeF₃ and 2 wt % of CaF₂ (Example 20). An experiment was carried outunder the same conditions as in Example 20 except that in this Example20, the charged raw material was changed to an alloy ofCa_(0.75)La_(2.6)Ce_(0.1)Si₆ (Example 21). The charged raw materials forthe phosphors (alloy compositions) and the firing conditions, etc. inExamples 20 and 21 are shown in Table 7. Further, the evaluation resultsof properties of the obtained phosphors (emission properties, absorptionefficiency and object color) are shown in Table 8.

TABLE 7 Charged raw Firing conditions materials (alloy First flux Secondflux Third flux Ex. No. composition) Type Amount (%) Type Amount (%)Type Amount (%) Ex. 20 Ca₀₄₅La_(2.6)Ce_(0.1)Si₆ MgF₂ 6 CeF₃ 6 LaF₃ 2 Ex.21 Ca_(0.75)La_(2.6)Ce_(0.1)Si₆ MgF₂ 6 CeF₃ 6 LaF3 2

TABLE 8 Emission properties (455 nm excitation) Emission peak EmissionObject color Comp. wavelength Chromaticity Chromaticity Luminanceintensity Luminosity Chroma Ex. No. (nm) coordinate x coordinate y (%)(%) L* a* b* (a*² + b*²)^(0.5) Ex. 20 540 0.434 0.543 108 110 97 −15 7779 Ex. 21 553 0.462 0.524 109 111 94 −7 95 95 Note) Luminance (%):Relative value to luminance of YAG commercial product (P46-Y3) being100%. Emission intensity (%): Relative value to luminance of YAGcommercial product (P46-Y3) being 100%.

From the results in Examples 20 and 21, it is evident that when theamount of Ca in the alloy is changed from 0.45 to 0.75, the highluminance is maintained, while the chromaticity coordinate value x isremarkably increased.

The sample in this Example 21 was further subjected to washing with 1Nhydrochloric acid, and then the same chemical analysis as in Example A1was carried out, whereby it was found that the chemical formula of theobtained phosphor, wherein the amount of Si was 6 mol, was found to beCa_(0.10)La_(2.6)Ce_(0.29)Si₆N₁₁O_(0.05). This substantially agrees tox=0.03, y=0.05, z=0.29 and w1=w2=0.

Examples 22 to 24 Effects of Rare Earth Fluorides

An experiment was carried out under the same conditions as in Example 19except that in Example 19, the flux was changed to 6 wt % of MgF₂ and 6wt % of CeF₃ (Example 22). An experiment was carried out under the sameconditions as in Example 22 except that in this Example 22, the flux waschanged to 6 wt % of MgF₂, 6 wt % of CeF₃ and 6 wt % of GdF₃ (Example23). An experiment was carried out under the same conditions as inExample 22 except that in Example 22, the flux was changed to 6 wt % ofMgF₂, 6 wt % of CeF₃ and 3 wt % of YF₃ (Example 24). The firingconditions for the phosphors in Example 22 to 24 and the evaluationresults of properties of the obtained phosphors (emission properties)are shown in Table 9.

TABLE 9 Emission properties (455 nm excitation) Firing conditionsEmission First flux Second flux Third flux peak Amount Amount Amountwavelength Chromaticity Chromaticity Ex. No. Type (%) Type (%) Type (%)(nm) coordinate x coordinate y Ex. 22 MgF₂ 6 CeF₃ 6 546 0.445 0.537 Ex.23 MgF₂ 6 CeF₃ 6 GdF₃ 6 546 0.458 0.527 Ex. 24 MgF₂ 6 CeF₃ 6 YF₃ 3 5470.452 0.530

From the results in Examples 22 to 24, it is evident that YF₃ and GdF₃have effects to increase the chromaticity coordinate value x. From themeasurements by SEM-EDX, it was found that Gd and Y were introduced inthe crystal particles of such GdF₃ type phosphor (Example 23) and YF₃type phosphor (Example 24). In the crystal particles in Example 23, Gdwas found to have been introduced in an amount of about 0.14 mol to 6mol of Si. It is considered that Gd or Y was substituted for La topresent an influence over the crystal field in the vicinity of the Ceactivation element, so that the emission color was changed.

Examples 25 to 30 Types of Flux

Experiments were carried out in the same manner as in Example 1 exceptthat in Example 1, the temperature raising rate from 800° C. wasincreased to 10″C/min, the firing temperature was changed to 1,450° C.,and the flux was changed to MgF₂, LIE, NaCl, KCL, BaCl₂ or CaF₂(Examples 25 to 30). The firing conditions (fluxes) for the phosphorsand the evaluation results of properties of the obtained phosphors(emission properties) in Examples 25 to 30 are shown in Table 10.

TABLE 10 Emission properties Firing (455 nm excitation) conditionsEmission (flux) peak Amount wavelength Chromaticity Chromaticity Ex No.Type (%) (nm) coordinate x coordinate y Ex. 25 MgF₂ 3 542 0.433 0.536Ex. 26 LiF 3 546 0.442 0.530 Ex. 27 NaCl 3 556 0.444 0.530 Ex. 28 KCl 3554 0.446 0.529 Ex. 29 BaCl₂ 3 553 0.454 0.525 Ex. 30 CaF₂ 10 554 0.4430.530

From the results in Example 25 to 30, it is evident that relative toMgF₂, LiF, NaCl, KCL, BaCl₂ or CaF₂ has an effect to increase thechromaticity coordinate value x.

Examples 31 to 36

With respect to phosphors obtained in the same manner as in Example 1except that the firing conditions were changed to the conditions shownin Table 11, the effects of cleaning with an acid were studied (Examples31 to 36). The conditions for acid cleaning and the emission propertiesof these phosphors are shown in Table 12.

TABLE 11 Firing conditions Alloy Temp.- raw First flux Second fluxraising Firing Firing material Amount Amount rate temp. time Ex. No.Amount (g) Type (%) Type (%) (° C.) (° C.) (hr) Ex. 31 14 MgF₂ 6 CeF₃ 60.1 1550 15 Ex. 32 14 MgF₂ 6 CeF₃ 6 0.1 1550 15 Ex. 33 14 MgF₂ 6 CeF₃ 60.1 1550 15 Ex. 34 1 MgF₂ 6 — — 0.5 1500 40 Ex. 35 1 MgF₂ 6 — — 0.5 150040 Ex. 36 1 MgF₂ 6 — — 0.5 1500 40 Note) Temperature-raising rate: Thetemperature raising rate (° C.) in a region of from 1,250 to 1,350° C.

TABLE 12-1 Emission properties (455 nm excitation) Emission Acidcleaning conditions peak Concentration wavelength ChromaticityChromaticity Luminance Emission Ex. No. Type of acid (wt %) Time (hr)(nm) coordinate x coordinate y (%) intensity (%) Ex. 31 — — — 545 0.4430.530 100 100 Ex. 32 NH₄HF₂  5 1 546 0.446 0.530 116 116 Ex. 33 NH₄HF₂10 1 546 0.443 0.531 109 109 Ex. 34 — — — 540 0.433 0.541 100 100 Ex. 35NH₄HF₂ 10 1 541 0.433 0.542 112 116 Ex. 36 HNO₃ 35 1 541 0.436 0.541 112116 Notes) —: Nil. Luminance (%): Relative value to luminance of aphosphor obtained under the same conditions without acid washing being100%. Emission intensity (%): Relative value to the emission strength ofa phosphor obtained under the same conditions without acid cleaningbeing 100%.

From the comparison of Examples 31 and 32, it is evident that whenammonium hydrogen fluoride (NH₄HF₂) is 5%, the relative luminanceincreases by 16% between before and after the treatment, and from thecomparison of Examples 31 and 33, the relative luminance increases by 9%when the ammonium hydrogen fluoride is 10%. From the results of Examples34 to 36, it is evident that when 35% nitric acid is used instead of 10%ammonium hydrogen fluoride, the luminance increases by 12% betweenbefore and after the treatment.

Example A1 Production of Alloy

La metal and Si metal were mixed and melted by an arc melting method inan argon atmosphere to obtain a LaSi alloy. This alloy was pulverized bya jet mill to obtain an alloy powder having a weight median diameter of7 μm.

Firing of Raw Material

In a glove box containing nitrogen as the operation atmosphere, 2.254 gof the alloy powder, 0.631 g of α-silicon nitride (SN-E10 manufacturedby Ube Industries, Ltd.) and 0.177 g of CeF₃ were mixed in an aluminamortar, and the mixture was filled in a molybdenum crucible having adiameter of 20 mm. After covering with a molybdenum foil, the cruciblewas set in an atmosphere firing electric furnace. After vacuuming fromroom temperature to 300° C., 4% hydrogen-containing nitrogen gas wasintroduced to ordinary pressure, and the temperature was raised to1,500° C. and maintained at 1,500° C. for 12 hours, followed by coolingto take out a fired product.

Treatment of Fired Product

The obtained fired product was pulverized in an alumina mortar, and theobtained powder was repeatedly stirred with 1 mol/L hydrochloric acid,cleaned, left to stand still and subjected to removal of thesupernatant, and further left to stand still for 1 day and night,followed by washing with water and drying to obtain a phosphor.

Evaluations

The production conditions and the evaluation results of properties(emission properties, absorption efficiency, object color, etc.) of thisphosphor are shown in Tables 12-5 and 12-6. Here, the luminance (%) andthe emission intensity (%) are relatively values to a YAG commercialproduct (P46-Y3 manufactured by Kasei Optonix) being 100%. The phosphorin Example A1 had a very high luminance of 137% to P46-Y3; a* and b*representing the object color were −19.4 and 81.3, respectively; thechroma (a*²+b*²)^(1/2) was high at 83.5; and the absorption efficiencywas very high at 92%.

As a result of the compositional analysis of this phosphor, the contentsof La, Ce, Si, N and O were 52.0, 3.74, 22.3, 20.9 and 1.0 wt %,respectively. On this basis, the molar ratio was calculated based on thetotal number of moles of La and Ce being 3,La:Ce:Si:N:O=2.8:0.2:6.0:11:0.47. Here, the contents of La, Ce and Siwere measured by an inductively coupled plasma atomic emissionspectroscopy by using a solution prepared by dissolving the phosphortreated by alkali fusion treatment. The contents of O and N weremeasured by means of an oxygen/nitrogen analyzer TC600 manufactured byLECO. It is considered that since this phosphor was sufficiently cleanedwith hydrochloric acid, a part of the phosphor was dissolved andconverted to an oxide or hydroxide, whereby oxygen was detected to someextent. Otherwise, the ratio of La, Ce, Si and N agreed to thecomposition of a (La,Ce)₃Si₆N₁₁ crystal.

The powder X-ray diffraction pattern of this phosphor is shown in FIG.4. A pattern was obtained which substantially agreed to No. 48-1805 ofICDD-JCPDS-PDF data which is a standard pattern of La₃Si₆N₁₁.

Examples A2 to A6

Phosphors were obtained by carrying out the same treatment as in ExampleA1 except that the composition of the raw material was changed asfollows.

TABLE 12-2 LaSi Si₃N₄ CeF₃ YH₃ YF₃ Ex. A2 2.254 0.631 0.177 0.165 0 Ex.A3 2.254 0.631 0.177 0.083 0.131 Ex. A4 2.254 0.631 0.177 0.083 0 Ex. A52.254 0.568 0.177 0.083 0.131 Ex. A6 2.254 0.732 0.177 0.083 0.131

The production conditions and the evaluation results of properties ofthe obtained phosphors are shown in Tables 12-5 and 12-6.

In Example A2, by the addition of YH₃, the emission wavelength shiftedtowards a long wavelength side, but the luminance, etc. weredeteriorated.

In Example A3, the same amount (molar amount) of Y as in Example A2 wasadded, but a part of YH₃ was added as YF₃, whereby the amount offluorine in the system was increased, and the crystal growth waspromoted, whereby the amount of Y taken into the phosphor was increased,and the emission wavelength shifted further to the long wavelength side.At the same time, the crystallinity became high, and the emissionintensity became higher than in Example A2.

In Example A4, the amount of YH₃ was made to be a half as compared withExample A2. The chromaticity coordinate x and the luminance becameintermediate values between Examples A1 and A2.

Example A5 represents a phosphor obtained by the same procedure as inExample A3 except that the amount of Si₃N₄ added was reduced. By thereduction of silicon nitride, the luminance and chroma decreasedsubstantially, and the reason is considered to be an increase ofbyproducts which hinder the emission.

Example A6 represents a phosphor obtained by the same procedure as inExample A3 except that the amount of Si₃N₄ added was increased. By theincrease of silicon nitride, the luminance and chroma were improved, andthe reason is considered to be a reduction of byproducts which hinderthe emission, contrary to Example A5.

Example A7

La metal and Si metal were mixed and melted by means of an arc meltingmethod in an argon atmosphere to obtain a LaSi alloy. In a glove boxcontaining nitrogen as an operation atmosphere, this alloy waspulverized in an alumina mortar and passed through a nylon mesh havingan aperture of 25 μm.

In a glove box containing nitrogen as an operation atmosphere, 7.032 gof such an alloy powder, 1.97 g of α-silicon nitride (SN-E10manufactured by Ube Industries, Ltd.) and 0.541 g of CeF₃ were mixed inan alumina mortar, and 3.1 g of this mixture was sampled and filled in amolybdenum crucible having a diameter of 20 mm. After covering with amolybdenum foil, the crucible was set in an atmosphere firing electricfurnace. After vacuuming from room temperature to 300° C., 4%hydrogen-containing nitrogen gas was introduced to ordinary pressure,and the temperature was raised to 1,500° C. and maintained at 1,500° C.for 12 hours, followed by cooling to take out a fired product.

The obtained fired product was pulverized in an alumina mortar, and theobtained powder was stirred and cleaned with 1 mol/L hydrochloric acid,followed by washing with water and drying to obtain a phosphor.

The production conditions and the evaluation results of properties(emission properties, absorption efficiency, object color, etc.) of thisphosphor are shown in Tables 12-5 and 12-6. This Example is one carriedout substantially in the same procedure as in Example A1, but thepulverization method of the alloy is different, whereby the propertyvalues such as the luminance and chroma were different to some extentfrom those in Example A1.

As a result of the compositional analysis of this phosphor, the contentsof La, Ce, Si, N and O were 53.0, 3.69, 22.3, 21.0 and 0.2 wt %,respectively. On this basis, the to molar ratios were calculated basedon the total number of moles of La and Ce being 3, wherebyLa:Ce:Si:N:O=2.8:0.2:5.9:11:0.08.

Here, the quantitative measurement was carried out in the same method ascarried out for the phosphor in Example A1. Thus, the results ofmeasurement which substantially agree to the desired composition of the(La,Ce)₃Si₆N₁₁ phosphor, were obtained. The powder X-ray diffractionpattern of this phosphor is shown in FIG. 5. A pattern whichsubstantially agrees to No. 48-1805 of ICDD-JCPDS-PDF data being astandard pattern of La₃Si₆N₁₁, was obtained.

Example A8

La metal and Si metal were mixed and melted by means of an arc meltingmethod in an argon atmosphere to obtain a LaSi alloy. This alloy waspulverized by a jet mill to obtain an ally powder having a weight mediandiameter of 10 μm. The raw materials were weighed in the followingweight ratio and mixed in an alumina mortar.

LaSi alloy=2.344 g, Si₃N₄=0.656 g, and CeF₃=0.18 g

The subsequent procedure was the same as in Example A1, and a phosphorwas produced. The production conditions and the evaluation results ofproperties of the obtained phosphor are shown in Tables 12-5 and 12-6.This phosphor was not subjected to cleaning treatment, and therefore,the luminance and chroma were inferior as compared with the phosphorsubjected to cleaning treatment with hydrochloric acid (the followingExample A9).

Example A9

The phosphor in Example A8 was put in 1 mol/L hydrochloric acid andstirred. It was washed with water and dried to obtain a phosphor. Theproduction conditions and the evaluation results of properties of theobtained phosphor are shown in Tables 12-5 and 12-6. The luminance ofthe phosphor in this Example was substantially the same as in ExampleA1, and the chroma of the phosphor in this Example was higher than thephosphor in Example A1.

Example A10

La metal and Si metal were mixed and dissolved by means of a highfrequency melting method in a water-cooled copper crucible in an argonatmosphere to obtain a LaSi alloy. This alloy was pulverized by a jetmill to obtain an alloy powder having a weight median diameter of 11 μm.The raw materials were weighed in the following weight ratio and mixedin an alumina mortar.

Using the mixture, a phosphor was produced by the same procedure as inExamples A8 and A9. The production conditions and the evaluation resultsof properties of the obtained phosphor are shown in Tables 12-5 and12-6.

Example A11

The respective metal raw materials were mixed so that the ratio of La,Ce, Y and Si became 0.42:0.03:0.05:0.5 and melted by means of an arcmelting method in an argon atmosphere to obtain a (La,Ce,Y)Si alloy.This alloy was pulverized in an alumina mortar in a glove box with anitrogen atmosphere and passed through a nylon mesh having an apertureof 37 μm.

Using this alloy, a phosphor was obtained by carrying out the sameprocedure as in Example A1 except that the blend raw materials andweight ratio were changed as follows.

(La,Ce,Y)Si alloy=2.328 g, Si₃N₄=0.672 g, and LaF₃=0.18 g

The production conditions and the evaluation results of properties ofthe obtained phosphor are shown in Tables 12-5 and 12-6.

Example A12

The respective raw materials were mixed so that the ratio of La, Ce, Yand Si became 0.42:0.03:0.05:0.5 and dissolved by means of a highfrequency melting method in a water-cooled copper crucible in an argonatmosphere to obtain a (La,Ce,Y)Si alloy. This alloy was pulverized by ajet mill to obtain an alloy powder having a weight median diameter of 12μm.

Using this alloy, a phosphor was obtained by carrying out the sameprocedure as in Example A1 except that the blend raw materials andweight ratio were changed as follows.

(La,Ce,Y)Si alloy=2.390 g, Si₃N₄=0.610 g, and LaF₃=0.18 g

The production conditions and the evaluation results of properties ofthe obtained phosphor are shown in Tables 12-5 and 12-6.

Example A13

La metal, Ce metal and Si metal were mixed so that the ratio of La:Ce:Sibecame 2.9:0.1:3.0 and melted by means of an arc melting method in anargon atmosphere to obtain a LaSi alloy. This alloy was pulverized by analumina mortar in a glove box with a nitrogen atmosphere and passedthrough a nylon mesh having an aperture of 25 μm.

In a glove box containing nitrogen as an operation atmosphere, 2.345 gof such an alloy powder, 0.656 g of α-silicon nitride (SN-E10manufactured by Ube Industries, Ltd.) and 0.180 g of CeF₃ were mixed inan alumina mortar, and the mixture was filled in a molybdenum cruciblehaving a diameter of 20 mm, and after covering with a molybdenum foil,the crucible was set in an atmosphere firing electric furnace. Aftervacuuming from room temperature to 300° C., 4% hydrogen-containingnitrogen gas was introduced to ordinary pressure, and the temperaturewas raised to 1,500° C. and maintained at 1,500° C. for 12 hours,followed by cooling to take out a fired product.

The obtained fired product was pulverized in an alumina mortar, and theobtained powder was put in 1 mol/L hydrochloric acid and stirred. Themixture was left to stand still for 1 day and night, and then, thesupernatant was removed, followed by washing with water and drying toobtain a phosphor. The production conditions and the evaluation resultsof properties (emission properties, absorption efficiency, object color,etc.) of this phosphor are shown in Tables 12-5 and 12-6.

Examples A14 to A17 and Comparative Example A1

Phosphors were obtained in the same manner as in Example A13 except thatthe composition of the alloy and the blend composition were changed asfollows.

TABLE 12-3 Alloy compositional ratio (La:Ce:Gd:Si) Blend amounts La CeGd Si Alloy Si₃N₄ CeF₃ LaF₃ Comp 2.7 0.3 0 3 2.344 0.655 0 0 Ex. A1 Ex.A14 2.7 0.3 0 3 2.344 0.656 0 0.179 Ex. A15 2.7 0.3 0 3 2.345 0.6560.180 0 Ex. A16 2.6 0.1 0.3 3 2.349 0.650 0 0.180 Ex. A17 2.4 0.3 0.3 32.349 0.651 0 0.180

The production conditions and the evaluation results of properties(emission properties, absorption efficiency, object color, etc.) of thephosphors are shown in Tables 12-5 and 12-6. The phosphor in ComparativeExample A1 had no fluoride added, and therefore, the luminance was low,and the chroma was also small.

By changing the amount of Ce in the raw materials as in Examples A14 andA15, it is possible to change the emission color (chromaticitycoordinates). By incorporation Ge to the alloy as in Examples A16 andA17, it is possible to change the emission color.

Example A18

La metal, Ce metal and Si metal were mixed so that the ratio of La:Ce;Sibecame 4.05:0.45:5.5 and melted by means of an arc melting method in anargon atmosphere to obtain a LaSi alloy. This alloy was pulverized by analumina mortar in a glove box with a nitrogen atmosphere and passedthrough a nylon mesh having an aperture of 25 μm.

In a glove box containing nitrogen as an operation atmosphere, 2.481 gof such an alloy powder, 0.520 g of α-silicon nitride (SN-E10manufactured by Ube Industries, Ltd.) and 0.180 g of LaF₃ were mixed inan alumina mortar, and the mixture was filled in a molybdenum cruciblehaving a diameter of 20 mm, and after covering with a molybdenum foil,the crucible was set in an atmosphere firing electric furnace. Aftervacuuming from room temperature to 300° C., 4% hydrogen-containingnitrogen gas was introduced to ordinary pressure, and the temperaturewas raised to 1,500° C. and maintained at 1,500° C. for 12 hours,followed by cooling to take out a fired product.

The obtained fired product was pulverized in an alumina mortar, and theobtained powder was put in 1 mol/L hydrochloric acid and stirred. Themixture was left to stand still for 1 day and night, and then, thesupernatant was removed, followed by washing with water and drying toobtain a phosphor.

The production conditions and the evaluation results of properties(emission properties, absorption efficiency, object color, etc.) of thisphosphor are shown in Tables 12-5 and 12-6.

Examples A19 to A22

Phosphors were obtained by treatment in the same manner as in ExampleA18 except that the composition of the alloy and the blend compositionwere changed as follows.

TABLE 12-4 Alloy compositional ratio (La:Ce:Si) Blend amounts (g) La CeSi Alloy Si₃N₄ LaF₃ Ex. A19 2.7 0.3 3 2.344 0.656 0.18 Ex. A20 4.5 0.5 42.226 0.774 0.18 Ex. A21 2.7 0.3 2 2.150 0.85 0.18 Ex. A22 4.5 0.5 32.112 0.888 0.18

The production conditions and the evaluation results of properties(emission properties, absorption efficiency, object color, etc.) ofthese phosphors are shown in Tables 12-5 and 12-6.

Phosphors in Examples A18 to A22 are ones prepared from raw materialsobtained by mixing an alloy having a different ratio of (La+Ce) and Si,and Si₃N₄ to obtain the desired phosphor composition, and further mixinga fluoride flux. It was found that even by using such raw materials, itwas possible to prepare a (La,Ce)₃Si₆N₁₁ phosphor.

Example A23

La metal and Si metal were mixed and melted by means of an arc meltingmethod in an argon atmosphere to obtain a LaSi alloy. This alloy waspulverized by an alumina mortar in a glove box with a nitrogenatmosphere and passed through a nylon mesh having an aperture of 37 μm.

In a glove box containing nitrogen as an operation atmosphere, 2.344 gof such an alloy powder, 0.656 g of α-silicon nitride (SN-E10manufactured by Ube Industries, Ltd.) and 0.180 g of CeF₃ were mixed inan alumina mortar, and the mixture was filled in a molybdenum cruciblehaving a diameter of 20 mm, and after covering with a molybdenum foil,the crucible was set in an atmosphere firing electric furnace. Aftervacuuming from room temperature to 300° C., 4% hydrogen-containingnitrogen gas was introduced to ordinary pressure, and the temperaturewas raised to 1,500° C. and maintained at 1,500° C. for 36 hours,followed by cooling to take out a fired product.

The obtained fired product was pulverized in an alumina mortar, and theobtained powder was put in 1 mol/L hydrochloric acid and stirred. Themixture was left to stand still for 1 day and night, and then, thesupernatant was removed, followed by washing with water and drying toobtain a phosphor.

Example A24

In the procedure of Example A23, the heating temperature and time werechanged to 1,550° C. for 12 hours, to obtain a phosphor.

TABLE 12-5 Production conditions Firing Retention Additives (in thebracket, molar temperature time Pulverization Alloy composition ratio toLa₃Si₆N₁₁ is indicated) (° C.) (hr) Ex. A1 Jet mill 7 μm LaSi CeF3(0.2)1500 12 Ex. A2 Jet mill 7 μm LaSi CeF3(0.2) + YH3(0.4) 1500 12 Ex. A3Jet mill 7 μm LaSi CeF3(0.2) + YH3(0.2) + YF3(0.2) 1500 12 Ex. A4 Jetmill 7 μm LaSi CeF3(0.2) + YH3(0.2) 1500 12 Ex. A5 Jet mill 7 μm LaSiCeF3(0.2) + YH3(0.2) + YF3(0.2) 1500 12 Ex. A6 Jet mill 7 μm LaSiCeF3(0.2) + YH3(0.2) + YF3(0.2) 1500 12 Ex. A7 Aperture 25 μm LaSiCeF3(0.2) 1500 12 Ex. A8 Jet mill 10 μm LaSi CeF3(0.2) 1500 12 Ex. A9Jet mill 10 μm LaSi CeF3(0.2) 1500 12 Ex. A10 Jet mill 11 μm LaSiCeF3(0.2) 1500 12 Ex. A11 Aperture 37 μm (La0.84Ce0.06Y0.1)Si CeF3(0.2)1500 12 Ex. A12 Jet mill 12 μm (La0.84Ce0.06Y0.1)Si CeF3(0.2) 1500 12Ex. A13 Aperture 25 μm (La2.9Ce0.1)Si3 CeF3(0.2) 1500 12 Comp. Ex. A1Aperture 25 μm (La2.7Ce0.3)Si3 Nil 1500 12 Ex. A14 Aperture 25 μm(La2.7Ce0.3)Si3 LaF3(0.2) 1500 12 Ex. A15 Aperture 25 μm (La2.7Ce0.3)Si3CeF3(0.2) 1500 12 Ex. A16 Aperture 25 μm (La2.6Ce0.1Gd0.3)Si3 LaF3(0.2)1500 12 Ex. A17 Aperture 25 μm (La2.4Ce0.3Gd0.3)Si3 LaF3(0.2) 1500 12Ex. A18 Aperture 25 μm (La4.05Ce0.45)Si5.5 LaF3(0.2) 1500 12 Ex. A19Aperture 25 μm (La2.7Ce0.3)Si3 LaF3(0.2) 1500 12 Ex. A20 Aperture 25 μm(La4.5Ce0.5)Si4 LaF3(0.2) 1500 12 Ex. A21 Aperture 25 μm (La2.7Ce0.3)Si2LaF3(0.2) 1500 12 Ex. A22 Aperture 25 μm (La4.5Ce0.5)Si3 LaF3(0.2) 150012 Ex. A23 Aperture 37 μm LaSi CeF3(0.2) 1500 36 Ex. A24 Aperture 37 μmLaSi CeF3(0.2) 1550 12

TABLE 12-6 Properties of phosphor Emission Emission peak ChromaticityChromaticity peak Internal Absorption External wavelength coordinatecoordinate Luminance intensity quantum efficiency quantum Reflectance(nm) value x value y (%) (%) yield (%) (%) yield (%) (770 nm) Ex. A1 5310.414 0.557 137 146 74.6 91.6 68.3 87.3 Ex. A2 538 0.431 0.544 110 11265.3 88.3 57.7 85.6 Ex. A3 545 0.443 0.538 117 122 66.5 92.2 61.3 84.1Ex. A4 537 0.426 0.548 120 123 67.2 91.0 61.1 85.8 Ex. A5 545 0.4460.534 87 89 52.0 88.9 46.3 77.0 Ex. A6 541 0.445 0.538 123 130 68.2 93.163.5 78.0 Ex. A7 535 0.427 0.551 128 134 67.3 94.4 63.5 80.5 Ex. A8 5330.420 0.552 103 107 55.1 89.8 49.4 84.1 Ex. A9 532 0.418 0.555 136 14466.5 94.4 62.8 84.0 Ex. A10 533 0.417 0.555 131 138 66.5 93.7 62.4 83.7Ex. A11 537 0.433 0.545 109 114 56.9 92.7 52.8 71.1 Ex. A12 540 0.4330.544 111 116 56.9 92.6 52.6 72.6 Ex. A13 533 0.420 0.554 124 131 67.791.0 61.6 82.8 Comp. 533 0.421 0.549 78 80 41.5 89.6 37.2 64.2 Ex. A1Ex. A14 534 0.423 0.553 124 131 67.7 92.1 62.4 82.2 Ex. A15 537 0.4340.546 118 123 64.2 93.5 60.0 81.5 Ex. A16 537 0.426 0.549 103 109 62.187.6 54.4 74.3 Ex. A17 542 0.442 0.540 107 113 59.6 92.3 55.0 72.6 Ex.A18 536 0.421 0.553 129 135 68.6 92.9 63.8 83.5 Ex. A19 533 0.423 0.553122 127 63.5 93.3 59.2 77.8 Ex. A20 535 0.422 0.552 121 127 64.8 92.559.9 80.5 Ex. A21 536 0.423 0.551 118 122 62.8 92.8 58.3 80.1 Ex. A22534 0.424 0.551 122 126 64.4 93.1 59.9 81.5 Ex. A23 533 0.419 0.555 132141 70.2 92.7 65.1 83.1 Ex. A24 533 0.415 0.556 126 134 72.5 88.9 64.585.6 Object color Luminosity L* a* b* Chroma (a*² + b*²)^(0.5) Ex. A199.43 −19.39 81.25 83.5 Ex. A2 96.17 −13.12 75.14 76.3 Ex. A3 97.2−12.89 85.96 86.9 Ex. A4 96.77 −14.68 78.87 80.2 Ex. A5 91.97 −8.5179.97 71.5 Ex. A6 96.41 −13.34 90.63 91.6 Ex. A7 96.91 −16.54 94.37 95.8Ex. A8 93.97 −13.53 73.32 74.6 Ex. A9 99.11 −19.03 89.4 91.4 Ex. A1097.96 −18.76 86.88 88.9 Ex. A11 92.55 −15.33 79.34 80.8 Ex. A12 92.97−15.15 77 78.5 Ex. A13 98.16 −18.45 81.78 83.8 Comp. Ex. A1 82.49 −10.7860.54 61.5 Ex. A14 97.32 −17.87 87.02 88.8 Ex. A15 95.73 −13.97 90.0291.1 Ex. A16 94.67 −17.12 72.87 74.9 Ex. A17 92.33 −13.51 85.07 86.1 Ex.A18 97.03 −18.09 84.76 86.7 Ex. A19 94.72 −17.32 86.04 87.8 Ex. A2096.23 −17.46 83.89 85.7 Ex. A21 85.69 −17.25 81.5 83.3 Ex. A22 96.08−16.63 84.88 86.5 Ex. A23 98.15 −19.07 89.43 91.4 Ex. A24 98.85 −19.0877.99 80.3

Examples 37 to 40 Production of Phosphor (LSCN)

A phosphor powder (LCSN) was obtained by carrying out an experiment inthe same manner as in Example 19 except that in Example 19, the flux waschanged to 6 wt % of MgF₂ and 6 wt % of CeF₃, and as a treatment afterthe firing, stirring/cleaning with 5N hydrochloric acid was added afterthe stirring/cleaning with the 10% NH₄HF₂ aqueous solution. The emissionproperties of this phosphor under excitation with 455 nm were such thatthe chromaticity coordinate value x was 0.451, the value y was 0.533,the emission peak wavelength was 546 nm, and the luminance to P46-Y3 was113%.

Production of Light-Emitting Device

A white light-emitting device was prepared by combining the obtainedphosphor (LCSN) and a short wavelength blue-emitting GAN type LED chip(ES-CEDBV15 manufactured by Epistar). Here, in order to disperse andseal the above phosphor powder, a sealing material silicone resin(SCR-1011 manufactured by Shin-Etsu Chemical Co., Ltd.) and a dispersant(REOLOSIL QS-30 manufactured by Tokuyama Corporation) were used. Aphosphor composition was prepared by adjusting the weight ratio of thephosphor (LCSN):the sealing material (SCR1011):the dispersant (QS30) tobe w:100:2, wherein w was as shown in Table 13. Such a mixture washeated at 70° C. for 1 hour and then heated at 150° C. for 5 hours forcuring to form a phosphor-containing portion thereby to obtain asurface-mounted type white light-emitting device.

Emission Properties

The spectrum characteristics of the obtained light-emitting device areshown in Table 13. As shown by the chromaticity coordinate values x andy in Table 13, it is evident that white emission can easily be realizedby only one type of this phosphor. In the case of white light of(x,y)=(0.330,0.327) in the light-emitting device in Example 38, theaverage color rendering evaluation number Ra was 68.2, and the emissionefficiency was 81.5 Lm/W. By changing the filling amount of LCSN, theemission color can be freely changed from a bluish white color to ayellowish white color.

TABLE 13 Mixing amounts of raw materials Amount Amount of of Ex. LCSNSCR1011 A SCR1011 B QS30 LCSN LED device No. (w) (g) (g) (g) (g) x yLumen Ex. 37 3 0.50 0.50 0.02 0.03 0.271 0.225 5.11 Ex. 38 6 0.50 0.500.02 0.06 0.330 0.327 5.30 Ex. 39 9 0.50 0.50 0.02 0.09 0.399 0.440 5.93Ex. 40 12 0.50 0.50 0.02 0.12 0.434 0.486 5.15 Short wavelength blue LEDLED device ES-CEDBV15) Luminous Emission Applied power efficiencyvoltage × (lm/W) (lm/W) Peak Applied Applied current Ex. (lumen/ (lumen/wavelength W1 voltage current W2 No. W1) W2) Ra (nm) (mW) (V) (mA) (mW)Ex. 37 238 77.5 69.8 441 21.48 3.30 20.0 66.0 Ex. 38 319 81.5 68.2 44216.59 3.30 19.7 65.0 Ex. 39 388 92.5 60.9 443 15.29 3.34 19.2 64.1 Ex.40 417 80.7 59.4 443 12.36 3.34 19.1 63.8

Examples 41 to 44 Production of Phosphor

A phosphor powder (LCSN) was obtained in the same manner as in Examples37 to 40.

Production of Light-Emitting Device

A white light-emitting device was prepared by combining the obtainedphosphor (LCSN) and a long wavelength blue-emitting GAN type LED chip(NL8436W manufactured by Showa Denko). Here, in order to disperse andseal the above phosphor powder, a sealing material silicone resin(SCR-1011 manufactured by Shin-Etsu Chemical Co., Ltd.) and a dispersant(REOLOSIL QS-30 manufactured by Tokuyama Corporation) were used. Aphosphor composition was prepared by adjusting the weight ratio of thephosphor (LCSN):the sealing material (SCR1011):the dispersant (QS30) tobe w:100:2, wherein w was as shown in Table 14. Such a mixture washeated at 70° C. for 1 hour and then heated at 150° C. for 5 hours forcuring to form a phosphor-containing portion thereby to obtain asurface-mounted type white light-emitting device.

Emission Properties

The spectrum characteristics of the obtained white light-emitting deviceare shown in Table 14. As shown by the chromaticity coordinate values xand y in Table 14, it is evident that white emission can easily berealized by only one type of this phosphor. Further, the emission colorcan freely be changed from bluish white to yellowish white by changingthe filling amount of LSCN. In the case of white light of (x,y)=(0.349,0.369) in the light-emitting device in Example 42, the average colorrendering evaluation number Ra was 68.3, and the emission efficiency was77.7 Lm/W. When compared with the same emission color, it is evidentthat the results in Table 13 using short wavelength blue LED showedhigher emission efficiency than the results in Table 14 using longwavelength blue LED.

TABLE 14 Mixing amounts of raw materials Amount Amount of of Ex. LCSNSCR1011 A SCR1011 B QS30 LCSN LED device No. (w) (g) (g) (g) (g) x yLumen Ex. 41 3 0.50 0.50 0.02 0.03 0.267 0.231 4.73 Ex. 42 6 0.50 0.500.02 0.06 0.349 0.369 5.19 Ex. 43 9 0.50 0.50 0.02 0.09 0.391 0.430 5.17Ex. 44 12 0.50 0.50 0.02 0.12 0.421 0.470 5.17 Long wavelength blue LEDLED device (NL8436W) Luminous Emission Applied power efficiency voltage× (lm/W) (lm/W) Peak Applied Applied current Ex. (lumen/ (lumen/wavelength W1 voltage current W2 No. W1) W2) Ra (nm) (mW) (V) (mA) (mW)Ex. 41 262 69.1 81.4 451 18.03 3.46 19.8 68.5 Ex. 42 288 77.7 68.3 45118.02 3.44 19.4 66.7 Ex. 43 293 75.9 63.5 451 17.66 3.46 19.7 68.2 Ex.44 286 75.8 61.3 451 18.05 3.44 19.8 68.1

Examples 45 to 48 Production of Phosphor (LCSN)

A phosphor powder (LCSN) was obtained in the same manner as in Examples37 to 40.

Production of Red Phosphor (SCASN)

The respective metals were weighed so that the metal elementcompositional ratio became Al:Si=1:1 (molar ratio). Using a graphitecrucible, the raw material metals were melted by means of a highfrequency melting furnace in an argon atmosphere and then poured fromthe crucible to a mold and solidified to obtain an alloy (matrix alloy)wherein the metal element compositional ratio was Al:Si=1:1.

The above matrix alloy and other raw material metals were weighed sothat the compositional ratio became Eu:Sr:Ca:Al:Si:0.008:0.792:0.2:1:1(molar ratio). The interior of the furnace was evacuated to 5×10⁻² Pa,then the evacuation was stopped, and argon was filled in the furnace toa prescribed pressure. In this furnace, the matrix alloy was melted in acalcia crucible, then Sr was melted, and the melt was poured from thecrucible into a mold and solidified to obtain a raw material alloy for aphosphor.

The raw material alloy for a phosphor thus obtained was roughlypulverized by an alumina mortar in a nitrogen atmosphere and thenpulverized by means of a supersonic jet pulverizer in a nitrogenatmosphere under a pulverization pressure of 0.15 MPa at a raw materialsupplying rate of 0.8 kg/hr. The obtained alloy powder was washed withwater, classified and dried to obtain a phosphor powder ofSr_(0.792)Ca_(0.200)AlEu_(0.008)SiN₃ (SCASN).

Production of Light-Emitting Device

A white light-emitting device was prepared by combining the obtainedphosphor (LCSN) and red phosphor (SCASN), and a longwavelength-blue-emitting GAN type LED chip (NL8436W manufactured byShowa Denko). Further, in order to disperse and seal the above phosphorpowder, a sealing material silicone resin (SCR-1011 manufactured byShin-Etsu Chemical Co., Ltd.) and a dispersant (REOLOSIL QS-30manufactured by Tokuyama Corporation) were used. A phosphor compositionwas prepared by adjusting the weight ratio of the phosphor (LCSN):thered phosphor (SCASN):the sealing material (SCR1011):the dispersant(QS30) to be u:v:100:2, respectively, wherein u and v are as shown inTable 15. Such a mixture was heated at 70° C. for 1 hour and then heatedat 150° C. for 5 hours for curing to form a phosphor-containing portionthereby to obtain a surface-mounted type white light-emitting device.

Emission Properties

The spectrum characteristics of the obtained white light-emitting deviceare shown in Table 15. As shown by the chromaticity coordinate values xand y in Table 15, it is evident that a white emission having a warmwhite color or light bulb color can easily be realized. In the case of awarm white light of (x,y)=(0.410,0.395) in the light-emitting device inExample 45, the average color rendering evaluation number Ra was 72.2.When compared with the same emission color to a combination of the longwavelength blue LED with only LCSN in the light-emitting device inExample 43, e.g. Ra63.5(x,y)=(0.391, 0.430) in the light-emitting devicein Example 43, it is evident that the color rendering property is higherwhen the red phosphor SCASN is combined.

TABLE 15 LED device Mixing amounts of raw materials Luminous EmissionAmount Amount Amount Amount power efficiency of of of of (lm/W) (lm/W)Ex. LCSN SCASN SCR1011 A SCR1011 B QS30 LCSN SCASN (lumen/ (lumen/ No.(u) (v) (g) (g) (g) (g) (g) x y Lumen W1) W2) Ra Ex. 45 6 1 0.50 0.500.2 0.06 0.01 0.410 0.395 4.78 271 70.5 72.2 Ex. 46 3 3 0.50 0.50 0.20.03 0.03 0.444 0.335 4.25 226 61.7 71.4 Ex. 47 6 2 0.50 0.50 0.2 0.060.02 0.459 0.401 4.75 273 73.2 72.1 Ex. 48 6 3 0.50 0.50 0.2 0.06 0.030.478 0.399 4.27 244 64.4 70.3 Long wavelength blue LED (NL8436W)Applied voltage × Ex. Peak wavelength Applied voltage Applied currentcurrent W2 No. (nm) W1 (mW) (V) (mA) (mW) Ex. 45 451 17.65 3.46 19.667.8 Ex. 46 451 18.79 3.46 19.9 68.9 Ex. 47 451 17.43 3.38 19.2 64.9 Ex.48 451 17.49 3.42 19.4 66.3

Examples 49 to 54 Production of Phosphor (LCSN)

A phosphor powder (LCSN) was obtained in the same manner as in Examples37 to 40.

Production of Blue Phosphor (BAM)

0.7 mol of barium carbonate (BaCO₃), 0.15 mol of europium oxide (Eu₂O₃),1 mol (as Mg) of basic magnesium carbonate (mass per 1 mol of Mg:93.17)and 5 mol of α-alumina (Al₂O₃) were weighed so that the composition ofthe respective raw materials charged for a phosphor would beBa_(0.7)Eu_(0.3)MgAl₁₀O₁₇, mixed for 30 minutes in a mortar and filledin an alumina crucible. This mixture was fired in a box type firingfurnace at 1,200° C. for 5 hours while supplying nitrogen, and aftercooling, the fired product was taken out from the crucible andpulverized to obtain a precursor for a phosphor. To this precursor, 0.3wt % of AlF₃ was added, then pulverized and mixed in a mortar for 30minutes, then filled in an alumina crucible and fired by a box typeatmosphere firing furnace at 1,450° C. for 3 hours in a nitrogen gascontaining 4 wt % of hydrogen, and after cooling, the obtained firedproduct was pulverized to obtain a pale blue powder.

To this powder, 0.42 wt % of AlF₃ was added, then pulverized and mixedfor 30 minutes in a mortar, then filled in an alumina crucible, and bysetting graphite in the beads form in a space around the crucible, firedat 1,550° C. for 5 hours by supplying nitrogen to the box type firingfurnace at a rate of 4 liters per minute. The obtained fired product waspulverized for 6 hours in a ball mill, then classified and subjected towater washing treatment to obtain a blue phosphor powder (BAM). Theobtained blue phosphor (BAM) had an emission peak wavelength of 455 nmand an emission peak full width at half maximum of 51 nm.

Production of Light-Emitting Device

A white light-emitting device was prepared by combining the obtainedphosphor (LCSN) and blue phosphor (BAM), and a near ultravioletlight-emitting GAN type LED chip (C395 MB290 manufactured by Cree).Here, in order to disperse and seal the above phosphor powder, a sealingmaterial silicone resin (U111 manufactured by Mitsubishi ChemicalCorporation) and a dispersant (Aerosil RX200 manufactured by NipponAerosil Co., Ltd.) were used. A phosphor composition was prepared byadjusting the weight ratio of the blue phosphor (BAN):the phosphor(LCSN):the sealing material (U111):the dispersant (RX200) to bep:q:100:15, wherein p and q are as shown in Table 16. Such a mixture washeated at 70° C. for 1 hour and then heated at 150° C. for 5 hours forcuring to form a phosphor-containing portion thereby to obtain asurface-mounted type white light-emitting device.

Emission Properties

The spectrum characteristics of the obtained white light-emitting deviceare shown in Table 16. As shown by the chromaticity coordinate values xand y in Table 16, it is evident that a high color rendering whiteemission from bluish white to yellowish white can easily be realized. Inthe case of white light of (x,y)=(0.321,0.361) in the light-emittingdevice in Example 52, the average color rendering evaluation number Rawas high at 78.3. As compared to a light-emitting device with acombination of the long wavelength blue LED with only LCSN in Example 42having the same emission color, Ra is of a value exceeding 68.3, and itis evident that the color rendering property is improved.

TABLE 16 LED device Mixing amounts of raw materials Luminous EmissionAmount Amount power efficiency Amount of Amount of (lm/W) (lm/W) Ex. ofBAM LCSN U111 RX200 of BAM LCSN (lumen/ (lumen/ No. (p) (q) (g) (g) (g)(g) x y Lumen W1) W2) Ra Ex. 49 9 3 1.00 0.15 0.09 0.03 0.278 0.311 1.78272 24.9 82.4 Ex. 50 9 6 1.00 0.15 0.09 0.06 0.294 0.329 1.70 264 22.681.7 Ex. 51 9 9 1.00 0.15 0.09 0.09 0.317 0.366 1.46 221 19.4 79.5 Ex.52 9 12 1.00 0.15 0.09 0.12 0.321 0.361 1.73 266 24.3 78.3 Ex. 53 12 81.00 0.15 0.12 0.08 0.417 0.492 1.76 271 24.5 64.8 Ex. 54 15 10 1.000.15 0.15 0.10 0.429 0.488 1.40 211 19.3 64.8 Near ultraviolet LED(C395MB290) Applied voltage × Ex. Peak wavelength Applied voltageApplied current current W2 No. (nm) W1 (mW) (V) (mA) (mW) Ex. 49 4006.53 3.74 19.1 71.4 Ex. 50 400 6.44 3.76 20.0 75.2 Ex. 51 400 6.61 3.7620.0 75.2 Ex. 52 400 6.51 3.74 19.1 71.4 Ex. 53 400 6.48 3.74 19.2 71.8Ex. 54 400 6.64 3.74 19.4 72.6

Examples 55 to 58 Production of Phosphor (LCSN)

A phosphor powder (LCSN) was obtained in the same manner as in Examples37 to 40.

Production of Blue Phosphor (BAM)

A blue phosphor powder (BAM) was obtained in the same manner as inExamples 49 to 54.

Production of Red Phosphor (CASON)

Ca₃N₂ (manufactured by CERAC, 200 mesh pass), AlN (Grade F manufacturedTokuyama Corporation), Si₃N₄ (SN-E10 manufactured Ube Industries, Ltd.)and Eu₂O₃ (manufactured by Shin-Etsu Chemical Co., Ltd.) were weighed sothat the molar ratio would be Eu:Ca:Al:Si=0.008:0.992:1:1.14 by anelectrobalance in a glove box filled with nitrogen with an oxygenconcentration of not more than 1 ppm. In this glove box, all of thesephosphor raw materials were pulverized and mixed for 20 minutes in analumina mortar until the mixture became uniform. The obtained rawmaterial mixture was filled in a boron nitride crucible and fired at1,800° C. for 2 hours under a nitrogen pressure of 0.5 MPa. Cleaning,dispersion and classification were carried out to obtain a red phosphorpowder (CASON) having a weight median diameter (D₅₀) of 8 μm to 10 μm.The composition of the obtained phosphor wasCa_(0.992)Eu_(0.008)AlSi_(1.14)N_(3.18)O_(0.01) by the chargedcomposition, the emission peak wavelength was 650 nm, and the full widthat half maximum was 92 nm.

Production of Light-Emitting Device

A white light-emitting device was prepared by combining the obtainedphosphor (LCSN), blue phosphor (BAM) and red phosphor (CASON), and anear ultraviolet light-emitting GAN type LED chip (C395MB290manufactured by Cree). Here, in order to disperse and seal the abovephosphor powder, a sealing material silicone resin (U111 manufactured byMitsubishi Chemical Corporation) and a dispersant (Aerosil RX200manufactured by Nippon Aerosil Co., Ltd.) were used. A phosphorcomposition was prepared by adjusting the weight ratio of the bluephosphor (BAN):the phosphor (LCSN):the red phosphor (CASON):the sealingmaterial (U111):the dispersant (RX200) to be r:s:t:100:15, wherein r, sand t are as shown in Table 17. Such a mixture was heated at 70° C. for1 hour and then heated at 150° C. for 5 hours for curing to form aphosphor-containing portion thereby to obtain a surface-mounted typewhite light-emitting device.

Emission Properties

The spectrum characteristics of the obtained white light-emitting deviceare shown in Table 17. As shown by the chromaticity coordinate values xand y in Table 17, it is evident that a high color rendering warm whiteor light bulb color emission can easily be realized. In the case of warmwhite light of (x,y)=(0.408, 0.417) in the light-emitting device inExample 55, the average color rendering evaluation number Ra was 77.1.As compared to the light-emitting device with a combination where noCASON was added in Example 53 having a similar emission color, Ra is ofa value exceeding 64.8, and it is evident that the color renderingproperty is improved.

TABLE 17 LED device Mixing amounts of raw materials Luminous EmissionAmount Amount Amount Amount power efficiency Amount of of Amount of of(lm/W) (lm/W) Ex. of BAM LCSN CASON U111 RX200 of BAM LCSN CASON (lumen/(lumen/ No. (r) (s) (t) (g) (g) (g) (g) (g) x y Lumen W1) W2) Ra Ex. 559 9 1 1.00 0.15 0.09 0.09 0.01 0.408 0.417 1.82 279 24.5 77.1 Ex. 56 156 1 1.00 1.15 0.15 0.06 0.01 0.448 0.458 1.59 249 21.9 71.4 Ex. 57 9 3 31.00 0.15 0.09 0.03 0.03 0.465 0.363 1.55 232 21.4 74.4 Ex. 58 9 6 31.00 0.15 0.09 0.06 0.03 0.469 0.368 1.46 218 19.4 74.4 Near ultravioletLED (C395MB290) Applied voltage × Ex. Peak wavelength Applied voltageApplied current current W2 No. (nm) W1 (mW) (V) (mA) (mW) Ex. 55 4006.53 3.76 19.8 74.4 Ex. 56 400 6.38 3.74 19.4 72.6 Ex. 57 400 6.68 3.7419.3 72.2 Ex. 58 400 6.72 3.76 20.0 75.2

Examples 59 and 60 Production of Phosphor (LCSN)

A phosphor powder (LCSN) was obtained in the same manner as in Examples37 to 40.

Production of Blue Phosphor (BAM)

A blue phosphor powder (BAM) was obtained in the same manner as inExamples 49 to 54.

Production of Green Phosphor (BSON)

As raw material compounds, BaCO₃ (267 g), SiO₂ (136 g) and Eu₂O₃ (26.5g) were sufficiently stirred and mixed so that the composition ofrespective raw materials charged for a phosphor would beBa_(2.7)Eu_(0.3)Si_(6.9)O₁₂N_(3.2) and then filled in an alumina mortar.This mixture was placed in a resistance-heating system electric furnaceprovided with a temperature controller, then heated at a temperatureraising rate of 5° C./min to 1,100° C. under atmospheric pressure andheld at that temperature for 5 hours and then left to cool to roomtemperature. The obtained sample was pulverized in an alumina mortar toat most 100 μm.

The sample (295 g) obtained as described above and Si₃N₄ (45 g) as a rawmaterial compound were sufficiently stirred and mixed, and then, for thefirst firing, filled in an alumina crucible. This mixture was heated to1,200° C. under atmospheric pressure, while supplying a mixed gas of 96vol % of nitrogen and 4 vol % of hydrogen at a rate of 0.5 L/min andmaintained at that temperature for 5 hours, and then left to cool toroom temperature. The obtained fired powder was pulverized in an aluminamortar to at most 100 μm.

300 g of the fired powder obtained by the above first firing, BaF₂ (6 g)as a flux and BaHPO₄ (6 g) were sufficiently stirred and mixed, thenfilled in an alumina mortar, and then, as the second firing, heated to1,350° C. under atmospheric pressure while supplying a mixed gas of 96vol % of nitrogen and 4 vol % of hydrogen at a rate of 0.5 L/min andheld at that temperature for 8 hours, and then left to cool to roomtemperature. The obtained fired powder was pulverized in an aluminamortar to at most 100 μm.

The sample (70 g) obtained by the above second firing, BaCl₂ (5.6 g) asa flux and BaHP₄ (3.5 g) were sufficiently stirred and mixed, thenfilled in an alumina mortar, and then, as the third firing, heated to1,200° C. under atmospheric pressure, while supplying a mixed gas of 96vol % of nitrogen and 4 vol % of hydrogen at a rate of 0.5 L/min andheld at that temperature for 5 hours, and then left to cool to roomtemperature. The obtained fired powder was slurried and dispersed bymeans of glass beads, then sieved to at most 100 μm, followed bycleaning treatment, and then, by using a calcium solution and aphosphate solution, surface coating with a calcium phosphate was carriedout.

2 g of the obtained phosphor was heated to 700° C. in about 40 minutesin atmospheric air by means of a quartz container having a diameter of30 mm and held at 700° C. for 10 minutes, whereupon the quartz containerwas taken out from the furnace and cooled to room temperature on a heatresistant brick to obtain a green phosphor powder (BSON).

Production of Red Phosphor (CASON)

A red phosphor powder (CASON) was obtained in the same manner as inExamples 55 to 58.

Production of Light-Emitting Device

A white light-emitting device was prepared by combining the obtainedphosphor (LCSN), blue phosphor (BAM), green phosphor (BSON), and redphosphor (CASON), and a near ultraviolet light-emitting GAN type LEDchip (C395 MB290 manufactured by Cree). Here, in order to disperse andseal the above phosphor powder, a sealing material silicone resin (U111manufactured by Mitsubishi Chemical Corporation) and a dispersant(Aerosil RX200 manufactured by Nippon Aerosil Co., Ltd.) were used. Aphosphor composition was prepared by adjusting the weight ratio of theblue phosphor (BAN):the green phosphor (BSON):the phosphor (LCSN):thered phosphor (CASON):the sealing material (U111):the dispersant (RX200)to be h:k:l:m:100:2, wherein h, k, l and m are as shown in Table 18.Such a mixture was heated at 70° C. for 1 hour and then heated at 150°C. for 5 hours for curing to form a phosphor-containing portion therebyto obtain a surface-mounted type white light-emitting device.

Emission Properties

The spectrum characteristics of the obtained white light-emitting deviceare shown in Table 18. As shown by the chromaticity coordinate values xand y in Table 18, it is evident that a high color rendering warm whiteor light bulb white emission can easily be realized. In the case of alight bulb color emission of (x,y)=(0.442, 0.426) in the light-emittingdevice in Example 60, the average color rendering evaluation number Rawas high at 83.1. As compared to the light-emitting device with acombination where no BSON was added in Example 56 having a similaremission color, Ra is of a value exceeding 71.4, and it is evident thatthe color rendering property is very much improved.

TABLE 18 Mixing amounts of raw materials Amount Amount Amount AmountAmount Amount Amount of of of Amount of of of Ex. of BAM BSON LCSN CASONU111 RX200 of BAM BSON LCSN CASON No. (h) (k) (l) (m) (g) (g) (g) (g)(g) (g) Ex. 59 15 1 1 1 1.00 0.15 0.15 0.01 0.01 0.01 Ex. 60 9 6 3 31.00 0.15 0.09 0.06 0.03 0.03 LED device Near ultraviolet LED(C395MB290) Luminous Emission Applied power efficiency voltage × (lm/W)(lm/W) Peak Applied Applied current Ex. (lumen/ (lumen/ wavelength W1voltage current W2 No. x y Lumen W1) W2) Ra (nm) (mW) (V) (mA) (mW) Ex.59 0.411 0.432 2.03 309 28.3 82.2 400 6.55 3.74 19.1 71.4 Ex. 30 0.4420.426 1.56 241 21.9 83.1 400 6.49 3.74 19.1 71.4

Comparative Example 6

A LED device disclosed in Example 39 in JP-A-2008-285659 is presented asComparative Example 6 in this application. The LED device in thisComparative Example is one obtained by combining a phosphor (oneobtained by firing a mixture of CaSiN₂ powder, lanthanum nitride powder,cerium oxide powder, silicon nitride powder and 0.5 wt % of CaF₂ flux at2,000° C. for 5 minutes under nitrogen pressure of 0.92 MPa and having acharged composition of Ca_(0.75)La_(2.4)Ce_(0.1)Si₆N₁₁) and ablue-emitting GAN type LED chip (460EZ manufactured by Cree). The curingconditions are the same as in Example 37. The raw material mixingamounts, the emission properties, etc. of the light-emitting device inComparative Example 6 are shown in Table 19.

In the light-emitting device in Comparative Example 6, a white light of(x,y)=(328,313) was obtained, and its luminous power was 281 Lm/W. Theluminous power in the light-emitting device in Example 38 having asimilar emission color is 319 Lm/W, which is higher than in ComparativeExample 6, and it is evident that one having the phosphor of the presentinvention mounted on LED is capable of emitting brighter white lightunder the same output condition.

TABLE 19 LED device Luminous Short Comp. Mixing amounts of raw powerwavelength Ex. materials (weight ratio) (lm/W) blue LED No. LCSN SCR1011QS30 x y Lumen (lumen/W1) W1 (mW) Comp. 4 97 3 0.328 0.313 1.57 281 5.58Ex. 6 Note) Short wavelength blue LED: 460EZ manufactured by Cree

Example 61 Production of Alloy

The respective metal raw materials of La solid metal blank, Ce solidmetal blank and Si solid metal blank were weighed so that the metalelement compositional ratio would be La:Ce:Si=2.9:0.1:6 (molar ratio),gently mixed and introduced into an arc melting furnace (ACM-CO1Pmanufactured by DIAVAC Limited). After evacuating the interior of thefurnace to 1×10⁻² Pa, argon was introduced, and the mixture was meltedby conducting an electric current of about 100 mA to the raw materialmetals in an argon atmosphere. After confirming that the molten metalwas sufficiently rotated by the principle of electromagnetic induction,application of the current was stopped, and the molten metal wasnaturally cooled and solidified to obtain an alloy for a phosphor rawmaterial. The obtained alloy for a phosphor raw material was confirmedto be a uniform alloy having the above metal element compositional ratioby SEM-EDX. By means of an alumina mortar and a nylon mesh sieve, thealloy for a phosphor raw material was pulverized to an alloy powderhaving a particle size of at most 37 μm, which was used as a rawmaterial for nitriding treatment.

Firing of Raw Material

In a glove box containing nitrogen as an operation atmosphere, 1 g ofsuch an alloy powder and 0.06 g of CeF₃ (6 wt % to the alloy rawmaterial) were mixed in an alumina mortar, and the mixture was pressedon a molybdenum tray having a diameter of 30 mm and set in an electricfurnace with a molybdenum inner wall having a tungsten heater. Aftervacuuming from room temperature to 120° C., 4% hydrogen-containingnitrogen gas was introduced to ordinary pressure, and while maintainingthe supply rate of 0.5 L/min, the temperature was raised to 800° C., andthen the temperature was raised at 0.5° C./min within ranges of from800° C. to 1,250° C. and from 1,350° C. to 1,550° C., and at 0.1° C./minwithin a range of from 1,250° C. to 1,350° C., and then firing wascarried out at 1,550° C. for 15 hours, followed by pulverization in analumina mortar.

Treatment of Fired Product

The obtained fired product was pulverized in an agate mortar, and theobtained powder was stirred and cleaned with a NH₄HF₂ aqueous solutionhaving a concentration of 10 wt % for 1 hour, then washed with water,and then stirred and cleaned with 5N hydrochloric acid for 1 hour andthen dried to obtain a phosphor. The evaluation results of properties(emission properties and object color) of this phosphor are shown inTable 20. Here, in Table 20, the luminance (%) and the emissionintensity (%) are relative values to a YAG commercial product (P46-Y3manufactured by Kasei Optonix) being 100%.

The phosphor in Example 61 had a luminance as high as 121% to P46-Y3; a*and b* representing the object color were −17 and 82, respectively; andthe chroma (a*²+b*²)^(1/2) was very high at 84. On the other hand,evaluation was carried out without treatment with the NH₄HF₂ aqueoussolution or hydrochloric acid, whereby the luminance to P46-Y3 was 92%.

Examples 62 to 68

Experiments were all carried out in the same manner as in Example 61except that in Example 61, the composition of the raw material alloy waschanged from La_(2.9)Ce_(0.1)Si₆ to the compositions disclosed in linesfor Examples 62 to 68 in Table 20. The evaluation results of properties(emission properties and object color) of the obtained phosphors areshown in Table 20.

With phosphors obtained by using, as the raw material, an alloycontaining e.g. Gd, Y or Sc, or an alloy having the amount of Ceincreased from 0.15 to 0.45, the chromaticity coordinate value x isincreased from 0.425 to 0.431 or 0.458, which indicates effectiveness tomake the emission color to be genuine yellow. Of these phosphors(Examples 62 to 68), a* and b* are from −8 to −14 and from 73 to 88,respectively, and the chroma (a*²+b*²)^(1/2) is very high at from 73 to89, which indicates that they are phosphors having a good object color.

The blue emission intensity due to a Ce-activated LaSi₃N₅ type byproductslightly included in the phosphors (Examples 61, 65 and 66) obtained byusing, as the raw material, La_(2.9)Ce_(0.1)Si₆,La_(2.75)Gd_(0.15)Ce_(0.1)Si₆, and La_(2.6)Gd_(0.3)Ce_(0.1)Si₆,respectively, becomes 9.6%, 5.9% and 5.9%, respectively, as representedby the relative intensity to the yellow emission intensity of P46-Y3excited with 455 nm, which indicates that is effective to substantiallyprevent blue emission due to the Ce-activated LaSi₃N₅ type.

TABLE 20 Raw material alloy La(_(3−x−y))A_(x)B_(y)Si₆ Firing Emissionproperties (455 nm excitation) Metal Metal condition Emission RelativeEmission element A element B Flux peak luminance intensity Ex. MolarMolar Amount wavelength Chromaticity Chromaticity to P46-Y3 to P46- No.Type ratio x Type ratio y Type (wt %) (nm) coordinate x coordinate y (%)Y3 (%) Ex. 61 Ce 0.1 — 0 CeF₃ 6 535 0.425 0.551 121 126 Ex. 62 Ce 0.15 —0 CeF₃ 6 536 0.431 0.547 115 119 Ex. 63 Ce 0.3 — 0 CeF₃ 6 537 0.4380.543 113 118 Ex. 64 Ce 0.45 — 0 CeF₃ 6 544 0.444 0.539 107 111 Ex. 65Ce 0.1 Gd 0.15 CeF₃ 6 541 0.442 0.540 99 102 Ex. 66 Ce 0.1 Gd 0.3 CeF₃ 6542 0.448 0.536 96 101 Ex. 67 Ce 0.1 Y 0.3 CeF₃ 6 545 0.450 0.534 93 98Ex. 68 Ce 0.1 Sc 0.3 CeF₃ 6 547 0.458 0.528 76 80 Object color Ex.Luminosity Chroma No. L* a* b* (a*² + b*²)^(0.5) Ex. 61 96 −17 82 84 Ex.62 93 −14 85 86 Ex. 63 92 −13 88 89 Ex. 64 89 −10 85 86 Ex. 65 88 −12 8182 Ex. 66 85 −11 78 79 Ex. 67 86 −11 79 80 Ex. 68 78 −8 73 73

As is apparent from the foregoing results, it has been found that alight-emitting device using the phosphor of the present invention isprovided with properties which are useful for practically advantageousapplications.

INDUSTRIAL APPLICABILITY

Uses of the phosphor of the present invention are not particularlylimited, and it is useful in various fields in which a usual phosphor isemployed. However, by utilizing the characteristic such that it isexcellent in the temperature properties, it is suitable for the purposeof realizing an illuminant for common illumination to be excited by alight source such as near ultraviolet LED or blue LED. Further, thelight-emitting device of the present invention employing the phosphor ofthe present invention having the above characteristic, is useful invarious fields in which a usual light-emitting device is employed.However, it is particularly useful as a light source for an imagedisplay device or a lighting device.

This application is a continuation of PCT Application No.PCT/JP2010/055934, filed Mar. 31, 2010, which is based upon and claimsthe benefit of priority from Japanese Patent Application No. 2009-086840filed on Mar. 31, 2009 and Japanese Patent Application No. 2009-236147filed on Oct. 13, 2009. The contents of those applications areincorporated herein by reference in its entirety.

REFERENCE SYMBOLS

-   -   1: Second illuminant    -   2: Surface-emitting GaN type LD    -   3: Substrate    -   4: Light-emitting device    -   5: Mount lead    -   6: Inner lead    -   7: First illuminant    -   8: Phosphor-containing resin portion    -   9: Conductive wire    -   10: Molded component    -   11: Surface-emitting lighting system    -   12: Casing    -   13: Light-emitting device    -   14: Diffuser panel    -   22: First illuminant    -   23: Second illuminant    -   24: Frame    -   25: Conductive wire    -   26, 27: Electrodes

1. A phosphor containing a crystal phase represented by the followingformula [I], wherein when its object color is expressed by the L*a*b*color system, the values of a*, b* and (a*²+b*²)^(1/2) satisfy−20≦a*≦−2, 71≦b* and 71≦(a*²+b*²)^(1/2), respectively:R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(w1+w2)O_(y+w1)N_(11−y−w1)  [I]wherein R is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc; M is at least one metal elementselected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is atleast one bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical valueswithin the following ranges, respectively:( 1/7)≦(3−x−y−z+w2)/6<(½),0≦(1.5x+y−w2)/6<(9/2),0≦x<3,0≦y<2,0<z<1,0≦w1≦5,0≦w2≦5,0≦w1+w2≦5.
 2. The phosphor according to claim 1, wherein0<(1.5x+y−w2)/6<( 9/2).
 3. The phosphor according to claim 1, whereinthe values of b* and (a*²+b*²)^(1/2) satisfy 71≦b*≦105 and71≦(a*²+b*²)^(1/2)≦105, respectively
 4. The phosphor according to claim1, wherein x is 0<x<3.
 5. The phosphor according to claims 1, wherein0≦(1.5x+y−w2)<(9/2).
 6. The phosphor according to claim 1, wherein theabsorption efficiency is at least 88%.
 7. A method for producing aphosphor containing a crystal phase represented by the following formula[I], which comprises nitriding an alloy for production of a phosphor,containing at least elements of R, A and Si, wherein said alloy issubjected to firing in the presence of a flux:R_(3−x−y−z+w2)M_(z)A_(1.5x+y−w2)Si_(6−w1−w2)Al_(w1+w2)O_(y+w1)N_(11−y−w1)  [I]wherein R is at least one rare earth element selected from the groupconsisting of La, Gd, Lu, Y and Sc; M is at least one metal elementselected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is atleast one bivalent metal element selected from the group consisting ofBa, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical valueswithin the following ranges, respectively:( 1/7)≦(3−x−y−z+w2)/6<(½),0≦(1.5x+y−w2)/6<(9/2),0≦x<3,0≦y<2,0<z<1,0≦w1≦5,0≦w2≦5,0≦w1+w2≦5.
 8. The method for producing a phosphor according to claim 7,wherein 0<(1.5x+y−w2)/6<(9/2).
 9. The method for producing a phosphoraccording to claim 7, wherein 0≦(1.5x+y−w2)<(9/2).
 10. The method forproducing a phosphor according to claim 7, wherein the firing is carriedout under a temperature condition such that the rate of temperature riseduring the firing is at most 0.5° C./min within a temperature rangecorresponding to at least a part of the low temperature side of anexothermic peak obtainable by TG-DTA (Thermogravimetry/DifferentialThermal Analysis) during the nitriding reaction of the alloy forproduction of a phosphor.
 11. The method for producing a phosphoraccording to claim 7, wherein the firing is carried out in ahydrogen-containing nitrogen gas atmosphere.
 12. The method forproducing a phosphor according to claim 7, wherein after the firing, theobtained fired product is washed with an acidic aqueous solution.
 13. Aphosphor containing a composition represented by the following formula[I], wherein when its object color is expressed by the L*a*b* colorsystem, the values of a*, b* and (a*²+b*²)^(1/2) satisfy −20≦a*≦−2,71≦b* and 71≦(a*²+b*²)^(1/2), respectively:(Ln,Ca,Ce)_(3+α)Si₆N₁₁  [I′] wherein Ln is at least one rare earthelement selected from the group consisting of La, Gd, Lu, Y and Sc, andα is a numerical value within a range of −0.1≦α≦1.5.
 14. Aphosphor-containing composition comprising the phosphor as defined inclaim 1 and a liquid medium.
 15. A light-emitting device having a firstilluminant and a second illuminant which emits visible light underirradiation with light from the first illuminant, wherein the secondilluminant contains, as a first phosphor, at least one phosphor selectedfrom the group consisting of the phosphor as defined in claim
 1. 16. Thelight-emitting device according to claim 15, wherein the first phosphorhas an emission peak wavelength within a wavelength range of from 420 nmto 450 nm.
 17. The light-emitting device according to claim 15, whereinthe second illuminant contains, as a second phosphor, at least onephosphor different in the emission peak wavelength from the firstphosphor.
 18. The light-emitting device according to claim 15, whereinthe first phosphor has an emission peak within a wavelength range offrom 420 nm to 500 nm, and the second illuminant contains, as a secondphosphor, at least one phosphor having an emission peak within awavelength range of from 565 nm to 780 nm.
 19. The light-emitting deviceaccording to claim 15, wherein the first phosphor has an emission peakwithin a wavelength range of from 300 nm to 420 nm, and the secondilluminant contains, as a second phosphor, at least one phosphor havingan emission peak within a wavelength range of from 420 nm to 500 nm. 20.The light-emitting device according to claim 15, wherein the firstphosphor has an emission peak within a wavelength range of from 300 nmto 420 nm, and the second illuminant contains, as a second phosphor, atleast one phosphor having an emission peak within a wavelength range offrom 420 nm to 500 nm, at least one phosphor having an emission peakwithin a wavelength range of from 500 nm to 550 nm, and at least onephosphor having an emission peak within a wavelength range of from 565nm to 780 nm.
 21. A lighting system provided with the light-emittingdevice as defined in claim
 15. 22. An image display device provided withthe light-emitting device as defined in claim 15.